10 Mathematics Quarter 2 - Module 2 GRAPHING POLYNOMIAL FUNCTIONS Department of Education ● Republic of the Philippines Mathematics- Grade 10 Alternative Delivery Mode Quarter 2 - Module 2: GRAPHING POLYNOMIAL FUNCTIONS First Edition, 2020 Republic Act 8293, section 176 states that: No copyright shall subsist in any work of the Government of the Philippines. However, prior approval of the government agency or office wherein the work is created shall be necessary for exploitation of such work for profit. Such agency or office may, among other things, impose as a condition the payment of royalty. Borrowed materials (i.e., songs, stories, poems, pictures, photos, brand names, trademarks, etc.) included in this book are owned by their respective copyright holders. Every effort has been exerted to locate and seek permission to use these materials from their respective copyright owners. The publisher and authors do not represent nor claim ownership over them. Published by the Department of Education Secretary: Leonor M. Briones Development Team of the Module Author: Marjury R. Gallardo Reviewers: Rhodel A. Lamban, PhD Elbert R. Francisco, PhD Alicia P. Micayabas, PhD Teodoro P. Casiano Illustrator and Layout Artist: Marjury R. Gallardo Management Team Chairperson: Arturo B. Bayocot, PhD CESO III Regional Director Co-Chairpersons: Victor G. De Gracia Jr.PhD CESO V Asst. Regional Director Randolph B. Tortola, PhD, CESO IV Schools Division Superintendent Shambaeh A. Usman, PhD Assistant Schools Division Superintendent Mala Epra B. Magnaong, Chief, CLMD Neil A. Improgo, PhD EPS-LRMS Bienvenido U. Tagolimot, Jr., PhD EPS-ADM Members Elbert R. Francisco, PhD, Chief, CID Rhodel A. Lamban, PhD, EPS in Mathematics Rejynne Mary L. Ruiz, PhD, LRMDS Manager Jeny B. Timbal, PDO II Shella O. Bolasco, Division Librarian II Printed in the Philippines by Department of Education – Division of Bukidnon Office Address: Fortich St., Sumpong, Malaybalay City Telephone: (088) 813-3634 E-mail Address: bukidnon@deped.gov.ph 10 Mathematics Quarter 2 - Module 2 GRAPHING POLYNOMIAL FUNCTIONS This instructional material was collaboratively developed and reviewed by educators from public. We encourage teachers and other education stakeholders to email their feedback, comments, and recommendations to the Department of Education at bukidnon@deped.gov.ph. We value your feedback and recommendations. Department of Education-Division of Bukidnon ● Republic of the Philippines Table of Contents What This Module is About What I Need to Know How to Learn from this Module Icons of this Module Lesson 1: The Leading Coefficient Test What I Need to Know What I Know What’s In What’s New What Is It What’s More What I Have Learned What I Can Do Assessment Additional Activities 1 1 3 4 5 9 11 12 12 14 Lesson 2: Graphing Polynomial Functions What I Need to Know What I Know What’s In What’s New What Is It What’s More What I Have Learned What I Can Do Assessment Additional Activities 16 16 18 19 19 23 23 24 25 26 Summary 27 Post-Test 28 Key to Answers 30 References 39 What This Module is About This module has been designed to help both the teacher and the learner make learning Mathematics as simple as possible. From its title, the learner is expected to learn how to graph polynomial functions. The requirement to understand this module easily is the learner’s knowledge on polynomial equations. Mathematics helps us think logically and reason out analytically. The vision of this module is to help the learner understand further the idea of functions. Functions is everywhere. For example, the amount of medicine that a person should take depends on the age of a person. The medicine dose changes when the age is changed. Desmos graphing application and Microsoft M Notes to the Teacher: This module has been made with the thought of a teacher standing in front of the class for discussions as well as the thought of one-on-one setting. This module focuses in graphing polynomial functions in a step-by-step process. May this help you in organizing your lessons and discussing your lessons in detail. Notes to the Learner: This is your last year in Junior High School. You are now in Grade 10, therefore it is expected that you have mastered the basic skills and foundation in Mathematics for these are the weapons that will help you in this higher order thinking skills battlefield. Believe in yourself that you can do the activities given in this module. Enclosed here is the step-by-step process on learning how to graph polynomial functions. Be mindful of your answers and scores on the Pre-test and compare it to your Post-test for this will measure your understanding level on the lesson. You need to make it sure that you understand the flow of the lesson so that you can have a better feedback later on. As you begin, make it a commitment to yourself to answer each item completely. This is for you and whatever you have learned will complete the success of this module. What I Need to Know Welcome to another learning experience! As you go through this module, you should be able to: identify the leading term, its leading coefficient and degree of polynomial function determine the end-behavior of the graph of polynomial function using the Leading Coefficient Test find the x and y intercepts of the function with the degree greater than 2 determine the turning points of the graph describe the multiplicity of roots on the graph sketch the graph of polynomial functions How to Learn from this Module To achieve the objectives cited above, you are to do the following: Take your time reading the lessons carefully. Follow the directions and/or instructions in the activities and exercises diligently. Answer all the given tests and exercises. Icons of this Module This module has the following parts and corresponding icons: What I Need to Know This will give you an idea of the skills or competencies you are expected to learn in the module. What I Know This part includes an activity that aims to check what you already know about the lesson to take. If you get all the answers correct (100%), you may decide to skip this module. What’s In This is a brief drill or review to help you link the current lesson with the previous one. What’s New In this portion, the new lesson will be introduced to you in various ways such as a story, a song, a poem, a problem opener, an activity or a situation. What is It This section provides a brief discussion of the lesson. This aims to help you discover and understand new concepts and skills. What’s More This comprises activities for independent practice to solidify your understanding and skills of the topic. You may check the answers to the exercises using the Answer Key at the end of the module. What I Have Learned This includes questions or blank sentence/paragraph to be filled into process what you learned from the lesson. What I Can Do This section provides an activity which will help you transfer your new knowledge or skill into real life situations or concerns. Assessment This is a task which aims to evaluate your level of mastery in achieving the learning competency. Additional Activities In this portion, another activity will be given to you to enrich your knowledge or skill of the lesson learned. This also tends retention of learned concepts. Answer Key This contains answers to all activities in the module. At the end of this module you will also find: References This is a list of all sources used in developing this module. The following are some reminders in using this module: 1. Use the module with care. Do not put unnecessary mark/s on any part of the module. Use a separate sheet of paper in answering the exercises. 2. Don’t forget to answer What I Know before moving on to the other activities included in the module. 3. Read the instruction carefully before doing each task. 4. Observe honesty and integrity in doing the tasks and checking your answers. 5. Finish the task at hand before proceeding to the next. 6. Return this module to your teacher/facilitator once you are through with it. If you encounter any difficulty in answering the tasks in this module, do not hesitate to consult your teacher or facilitator. Always bear in mind that you are not alone. We hope that through this material, you will experience meaningful learning and gain deep understanding of the relevant competencies. You can do it! PRE TEST Let us find out first what you have already probably known related to the content of this module. Choose to answer all the items. Select the letter of your choice. Take note of your wrong answers and find out what went wrong why you got such wrong answer. However, you may skip this lesson if you get a perfect score without any help from others. 1. To define a polynomial function, what should be n if f(x) = xn? A. any real number C. a negative integer B. a positive integer D. any integer 2. Give the leading coefficient of the polynomial function y = x3 – 4x2 – 2 ? A. 1 B. 2 C. 3 D. 4 3. The following are example of polynomial functions, EXCEPT? A. f(x) = 3x5 + x3 + 2x +4 C. f(x) = 2x-4 – 4 B. f(x) = 3x2 +4x +2 D. f(x) = x3 4. Which polynomial functions in factored form shows the sketch of the graph below? A. B. C. D. 5. Which of the following is the standard form of the polynomial function f(x) =-10x2 + 9 + x4? A. f(x) = 9 + x4-10x2 C. f(x) = 10x2 + x4 +9 B. f(x) = x4 + 9 +10x2 D. f(x) = x4 -10x2 + 9 6. Which of the choices below show the graph of polynomial function y = x3 – 7x + 6? A. B. c. D. 7. Which of the following represents a graph of a polynomial function? A. B. C. D. 8. What is the factored form of the polynomial function f(x)= x 3 – 6x2 + 11x – 6 A. f(x) = (x-1)(x-2)(x-3) B. f(x) = (x+1)(x+2)(x-3) C. f(x) = (x+1)(x-2)(x-3) D. f(x) = (x+1)(x+2)(x+3) 9. If the end behavior of a graph of the polynomial function falls both to the left and to the right, which of the following is true about the leading term? A. the leading coefficient is positive, the degree is odd B. the leading coefficient is positive, the degree is even C. the leading coefficient is negative, the degree is odd D. the leading coefficient is negative, the degree is even 10. What is the y-intercept of the function y = x3 – 4x2 + x + 6 A. 2 B. -3 C. 6 D. -6 11. Determine the end behavior of the polynomial function f(x) = x5 – 3x4 + 4 ? A. rises to the left, falls to the right B. rises to the right, falls to the left C. falls to both sides D. rises to both sides 12. If you are to illustrate the graph of the polynomial function y= -3x4 – 6x + 4, which will be your possible sketch? A. B. C. D. 13. A point where the function changes from decreasing to increasing or from increasing to decreasing values. A. Multiplicity of a Root C. Turning Points B. Intercept of a Graph D. Leading Coefficient Test 14. How will you sketch the graph of y = x (x-1)3 with respect to the x-axis? A. tangent at both (1,0) and (0,0) B. crossing (1,0) and tangent to (0,0) C. tangent at (1,0) and crossing (0,0) D. crossing both (1,0) and (0,0) 15. The following describes the graph of polynomial functions EXCEPT; A. smooth B. continuous C. rounded turns D. observable gaps Lesson 1 THE LEADING COEFFICIENT TEST What I Need to Know Welcome to another exciting topic on polynomial functions! This lesson is a pre-requisite to the next lesson which is the graphing of polynomial functions. In this lesson you are expected to: identify the leading term, its leading coefficient and the degree of polynomial functions. determine the end behavior of the graph of polynomial functions using the Leading Coefficient Test. What I Know This activity is to assess how much you have already known about the lesson. Choose the letter of your answer. Let your facilitator check your answers and take note of the missed items. However, you may skip this lesson if you get a perfect score without any help from others. 1. What is the leading term of the polynomial function y = -4x3 + x4 – 2x -3? A. -4x3 B. x4 C. 2x D. -3 2. Which polynomial functions in factored form shows the sketch of the graph below? A. B. C. D. 1 3. Which of the following is true about the leading coefficient and degree of y = x4 - 4x3 – 2x -3? A. positive, odd B. negative, even. C. positive, even. D. negative, odd 4. Which of the following graph represents a polynomial function? A. B. C. D. 5. Determine the end behavior of the graph of polynomial function f(x) = -x5 – 3x4 + 4? A. rises to the left, falls to the right B. rises to the right, falls to the left C. falls to both sides D. rises to both sides 6. What is the y-intercept of the function f(x) = A. -18 B. -9 C. -1 D. 9 ? 7.. What is the degree of the polynomial function y = A. 0 B. 1 C. 2 D. 3 ? 8. What is the y- intercept of the function y = x3 – 4x2 + 3x – 2? A. -4 B. -2 C. 2 D. 4 9. The following are example of polynomial functions, EXCEPT? A. f(x) = 3x5 + x3 + 2x +4 B. f(x) = 3x2 +4x +2 C. f(x) = 2x4 – 4 D. f(x) = x3 + 2/(x+4) 10. Which of the following graph could be the illustration of y= -3x4 – 6x + 4? A. B. C. 2 D. 11. If the end behavior of a graph of the polynomial function rises to the left and falls to the right, which of the following is true about the leading term? A. the leading coefficient is positive, the degree is odd B. the leading coefficient is positive, the degree is even C. the leading coefficient is negative, the degree is odd D. the leading coefficient is negative, the degree is even 12. To define a polynomial function, what should be n if f(x) = xn? A. a positive integer B. any real number C. a negative integer D. any integer 13. Which of the following is true about the graph below? A. the leading coefficient is positive, the degree is odd B. the leading coefficient is positive, the degree is even C. the leading coefficient is negative, the degree is odd D. the leading coefficient is negative, the degree is even 14. If the leading coefficient is positive and the degree is even, which would be its possible graph? A. B. C. D. 15. What is the degree of the polynomial function y = -4x3 + x4 – 2x -3? A. -4 B. -3 C. 3 D. 4 3 What’s In In order to get you ready in this lesson, do the next activity. It is about the concepts of polynomial function which you have learned in the previous module. Leading Term Polynomial Function Leading Coefficient Degree y = 3x4 – 8x3 + 8x – 6 1. 2. 3. y = -x4 + 16x + 2 4. 5. 6. y = x3 – 4x2 + x + 6 7. 8. 9. y = -2x5 + x3 – 7x2 + 4 10. 11. 12. What’s New Let’s explore! Observe the graphs given below and answer what is asked for each item. The first one is done for you. One point check is given in each blank. Leading term: anxn where an ≠ 0 Leading coefficient : an ˃ 0 positive an < 0 negative Degree : even or odd A. Polynomial function: y = x3 – 7x + 6 X Leading term: ___________ 1 Leading coefficient : __(Positive/Negative) 3 Degree :___(Even/Odd) Left: (Rise/Fall) Right: (Rise/Fall) 2 Number of turn point: _____ 3 4 B. Polynomial function: y= -3x3- 2x2 + 8x Leading term: ___________ Leading coefficient : ______________ Degree :______________ C. Polynomial functions: y = x4 – 3x2 – 3 Leading term: ___________ Leading coefficient : ______________ Degree :______________ D. Polynomial Functions: y = -3x2 – 6x + 4 Leading term: ___________ Leading coefficient : ______________ Degree :______________ E. Polynomial functions: f(x) = x3 + 4 Leading term: ___________ Leading coefficient : ______________ Degree :______________ Were you able to provide what is asked for each blank? Were you able 5 to recall the concept of polynomial function? Now that you have reviewed the important concepts of polynomial function, let us explore some methods on showing the graph of a polynomial function as you go What Is It The activity that you have just answered will lead you to the new topic which is The Leading Coefficient Test. This test can help you determine the end behavior of the graph of polynomial functions by looking at the degree and the leading coefficient so that it will give you a rough sketch of the graph. Let’s start by reviewing the definition of a polynomial function that you have learned in the previous topic. A polynomial function is a function of the form : F(x) = an xn + an-1 xn-1 + … + a1 x + a0 where an are real numbers called coefficients and n is a positive integer, and anxn is the leading term, an is the leading coefficient, a0 is the constant term and an ≠ 0. End behavior is a description of the values of the function as x approaches positive infinity or negative infinity. The leading coefficient and the degree of a polynomial function determine its end behavior and it is very much helpful in graphing polynomial function. Polynomial End Behavior Leading Coefficient Positive a>0 Degree Graph Comparison Even The graph rises to the right and rises to the left Negative a<0 Even The graph falls to the right and falls to the left 6 End Behavior Positive a>0 Odd The graph rises to the right and falls to the left Negative a<0 Odd The graph rises to the left and falls to the right. Here are the examples of the four cases of the Leading Coefficient Test. A. On the positive leading coefficient and even degree. Steps Expression 1. Look at the given polynomial function f(x)= 2x4 – 3x3 + x -1 2. Identify the leading term, its leading coefficient and degree 2x4 3. Identify the end behavior of the graph. 2x4 Discussion 2 is the leading coefficient and it is positive. 4 is the degree and it is an even number. The graph rises to the right and rises to the left 4. Graph The leading coefficient of the polynomial is positive and its degree is an even number. B. On the negative leading coefficient and even degree. Steps Expression 7 Discussion 1. Look at the given polynomial function f(x)= -3x2 – 6x + 4 2. Identify the leading term, its leading coefficient and degree -3x2 3. Identify the end behavior of the graph. 4.Graph -3x2 -3 is the leading coefficient and it is negative. 2 is the degree and it is an even number. The graph falls to the right and falls to the left The leading coefficient of the polynomial is negative, and its degree is an even number. C. On the positive leading coefficient and odd degree. Steps Expression 1. Look at the given polynomial function f(x)= x3 + 5 2. Identify the leading term, its leading coefficient and degree x3 3. Identify the end behavior of the graph. 4. Graph x3 Discussion 1 is the leading coefficient and it is positive. 3 is the degree and it is an odd number. The graph rises to the right and falls to the left The leading coefficient of the polynomial is positive and its degree is an odd number. D. On the negative leading coefficient and odd degree. Steps Expression Discussion 8 1. Look at the given polynomial function f(x)= -x5 + x4 -2x3 + 1 2. Identify the leading term, its leading coefficient and degree -x5 3. Identify the end behavior of the graph. -x5 -1 is the leading coefficient and it is negative. 5 is the degree and it is an odd number. The graph rises to the left and graph falls to the right. 4.Graph The leading coefficient of the polynomial is negative and its degree is an odd number. Were you able to understand the concept of the Leading Coefficient Test? Do you want more examples? Try to do the next activity. What’s More Let’s try this! Determine the end behavior of the graph of each polynomial function. Show your answer by filling in the blanks and show the possible sketch of the graph. The first one is made for you. One point check is given in each blank. Sketching the graph would earn 3 points. GUIDED PRACTICE A. y = -x4 + 10x2 - 9 1. The leading term is -x4 2. The leading coefficient is -1 and it is negative. 3. The degree is 4 and it is even. 4. Since the leading coefficient is negative and the degree is even, then the graph falls to the left and falls to the right. 5. Possible sketch: 9 B. y = -2x3 + x2 + 18x – 9 1. The leading term is ____ 2. The leading coefficient is ______ and it is _________. 3. The degree is _____ and it is ______. then 4. Since the leading coefficient is _________ and the degree is ____, the graph _______ to the left and _______ to the right. 5. Possible sketch: C. y = 4x3 – 4x2 – 19x +10 1. The leading term is ____ 2. The leading coefficient is ______ and it is _________. 3. The degree is _____ and it is ______. 4. Since the leading coefficient is _________ and the degree is ____, then the graph _______ to the left and _______ to the right. 5. Possible sketch: D. y = x4 – 10x2 + 9 1. The leading term is ____ 2. The leading coefficient is ______ and it is _________. 3. The degree is _____ and it is ______. 4. Since the leading coefficient is _________ and the degree is ____, then the graph _______ to the left and _______ to the right. 5. Possible sketch: 10 Have you answered the guided practice given above? If yes, very good! How was your score? So here are the remarks as to the number of scores that you got in the activity that you have just answered. If your score is: 36: You got the perfect score! 25-35 : You are doing great! Review your missed items and proceed to the next activity. 15-24: You are doing just fine but you need to gain mastery on the Leading Coefficient Test. 1-14 : Please consider study harder. Ask help form your friend or your teacher or even a relative to make you understand the concepts. Revisit the given examples and answer again. INDEPENDENT PRACTICE A. Identify whether the function graphed has positive or negative leading coefficient 1. 2. 3. 4. B. Determine whether the function graphed has an odd or even degree 5. 6. 7. 8. 11 What I Have Learned Now, in order to gain more mastery, complete the table below. Polynomial Functions Leading Coefficient (positive/negative) Degree (odd/ even) End behavior of the Graph Left side f(x) = 3x3 – 8x2 -8x +8 f(x) = -x4 - 6x3+9x2-6x+8 f(x) = -x3 – 4x2 + x+ 6 1. 2. 3. 4. 5. 6. 7. 8. 9. Possible Sketch Right side 10. 11. 12. 13. 14. 15. What I Can Do It’s time for you to check your understanding. Act like a detective and do the activity below. Read the situation and answer the questions that follow. Two students namely Amihan and Pirena were asked by their teacher to show the sketch of the graph of the polynomial function f(x) = x4 – 3x2 -3. Who among the two students show the graph correctly? Why do you say so? Explain your answer. PIRENA AMIHAN 12 Were you able to identify who between the two students graph it right? If yes, you did a great job! If no, try harder next time. Assessment If you wish to gain more mastery, try these activities below. GUIDED PRACTICE Identify the leading coefficient, degree and end-behavior. y = -4x4 – 3x3 + x2 +4 1. leading coefficient: 2. degree: 3. end behavior: y = 3x2 + 6x – 10 4. leading coefficient: 5. degree: 6. end behavior: 7 y= -2x + 6x5 + 2x3 7. leading coefficient 8. degree: 9. end behavior 5 y = x – 4x2 + 3x – 1 10. leading coefficient: 11. degree: 12. end behavior: y = 5.5x8 + 7.5x4 13. leading coefficient: 14. degree: 15. end behavior: INDEPENDENT PRACTICE 13 Identify whether the function graphed has an odd or even degree and a positive or negative leading coefficient. 1. 5. 9. 13. 2. 3. 6. 10. 14. 4. 7. 8. 11. 12. 15. 14 Additional Activities For your mastery on the Leading Coefficient Test, do the next activity below. Write the polynomial function indicated by the description in each item. Choose your answer from the box. f(x) = 5x3 + 9x + 1 f(x) = 2x6 + 3x4 + 5x2 f(x) = -4x2 + 3x -1 f(x) = -5x3 + x - 8 __________1. The end behavior of the graph of this polynomial function rises to both left and right. __________2. The end behavior of the graph of this polynomial function rises to the left and falls to the right. __________3. The leading coefficient is negative, and the degree is even. __________4. The leading coefficient is positive, and the degree is even. __________5. The end behavior of the graph of this polynomial function rises to the right and falls to the left. __________6. The leading coefficient is positive, and the degree is odd. __________7. The end behavior of the graph of this polynomial function falls to both left and right. __________8. The leading coefficient is negative, and the degree is odd. f(x) = 2x3 + 3x2 – 4x f(x) = -x5 + 5x4 + 1 f(x) = 3x6 + 4x5 - 2x + 4 f(x) = -3x4 + 8x2 + 5 15 __________9. The end behavior of the graph of this polynomial function rises to both left and right. __________10. The end behavior of the graph of this polynomial function rises to the left and falls to the right. __________11. The leading coefficient is negative, and the degree is even. __________12. The leading coefficient is positive, and the degree is even. __________13. The end behavior of the graph of this polynomial function rises to the right and falls to the left. __________14. The leading coefficient is positive, and the degree is odd. __________15. The end behavior of the graph of this polynomial function falls to both left and right. __________16. The leading coefficient is negative, and the degree is odd. 16 Lesson 2 GRAPHING POLYNOMIAL FUNCTIONS What I Need to Know This is it! You are now about to learn more on polynomial functions because as you go through this lesson, you should be able to: find the x and y intercepts of a polynomial function with degree greater than 2 determine the turning points of the graph describe the multiplicity of roots on the graph sketch the graph of polynomial functions What I Know Earlier in the study of your Grade 10 Mathematics, you learn about polynomials, the Factor Theorem, the Rational Root Theorem, the Remainder Theorem and the Fundamental Theorem of Algebra. This time answer the activity below for you to know how much you have already learned about the lesson. However, if you get a perfect score without 17 any help from others, you may skip this lesson. You can continue working all the activities in this lesson at your own desire. 1. Which of the following is the polynomial function given if the factored form is y = x(x+4)(x+1)(x-3)? A. y = x4 + 2x3 – 11x2 – 12x B. y = 2x3 – 11x2 – 12x C. y = 11x2 – 12x D. y = 11x3 – 12x 2. Which function represents the graph below? A. f(x) = x(x+4)(x+1)(x-3) B. f(x) = (x+4)(x+1)(x-3) C. f(x) = x(x+4)(x+2) D. f(x) = x(x+4)(x+2)(x-1) 3. Which of the following could be the graph of y = x3 – 3x2 – x + 3? A. B. C. D. 4. What is the factored form of the polynomial function y = x3 – 3x2 – x + 3? A. y = x(x-2)(x+2) B. y = (x+1)(x-3)(x-1) C. y = (x+1)(x-3)(x+1) D. y = (x+1)(x-3)(x-3) 5. What is the y – intercept of the function f(x) = x(x+4)(x+1)(x-3)? A. -4 B. -3 C. -1 D. 0 6. How many turning points does a cubic function with 3 real zeros have? A. -1 B. 0 C. 1 D. 2 7. Which polynomial function has zeros -1, 3, 1? A. y = (x+1)(x-3)(x+1) B. y = (x+1)(x-3)(x-3) C. y = (x+1)(x-3)(x-1) D. y = (x-1)(x-3)(x-1) 8. Which polynomial function has a y-intercept of 8? 18 A. f(x) = x3 + x2 – 10x + 8 B. f(x) = x3 + x2 – 10x – 8 C. f(x) = x3 + x2 – 10x – 4 D. f(x) = x3 + x2 – 10x + 4 9. What is the multiplicity of the root -1 in the equation y = x4-2x3-3x2+4x+4? A. 1 B. 2 C. 3 D. 4 10. What is the degree of the polynomial function y = 2x3-3x2+4x+4? A. 1 B. 2 C. 3 D. 4 11. What are the x-intercepts of the function y = x4 + x3 – 7x2 – x + 6? A. 1, -1, -3, 2 B. 1, -1, 2 C. 1, -1, 3 D. 1, -3, 2 12. Which of the following shows the graph of y = x(x+2)(x+1)? A. B. C. D. 13. If the end behavior of a graph of the polynomial function rises to the right and falls to the left, which of the following is true about the leading coefficient and its degree? A. negative, even B. positive, even C. negative, odd D. positive, odd 14. How will you sketch the graph of y = x (x-1)4 with respect to the x-axis? A. tangent at both (1,0) and (0,0) B. crossing (1,0) and tangent to (0,0) C. tangent at (1,0) and crossing (0,0) D. crossing both (1,0) and (0,0) 15. What is the leading coefficient of the function y = x4-2x3-3x2+4x+4? A. 1 B. 2 C. 3 D. 4 What’s In Here is another activity to hone your knowledge in finding the roots of polynomial functions. Find the factors of the given 19 polynomial function and write its roots on the last column. The first one is done for you. Polynomial Function 1. y = x4 + x3 - 7x2 – x + 6 Factors Roots y=(x+3)(x-2)(x+1)(x-1) -3,2,-1,1 2. y = x3 + 9x2 + 15x – 25 3. y = x4 + 4x3 – 13x2 -40x + 48 4. y = x4 + 6x3 – 9x2 - 54x 5. y = x4 – 9x3 –x2 + 9x How was it? It’s quiet challenging right? But of course if you have mastered synthetic division or the rational root theorem, it’s just a piece of cake! So let’s take a look at your score. if your score is: 8 : You are doing great! You have mastered the previous theorems 5-7: You are doing just fine but you need to practice more in order to gain mastery. 1-4 : Please consider study harder. Ask help form your friend or your teacher or even a relative to make you understand the concepts. Revisit the given examples and answer again. What’s New Using your graphing paper or graphing notebook, try to graph the function given below by plotting the values of x and y presented by the table. 1. f(x) = x2 X -3 -2 -1 0 1 2 3 y 9 4 1 0 1 4 9 2.f(x) = x3 X -3 -2 -1 0 1 2 3 y -27 -8 -1 0 1 8 27 20 Did you show the graph correctly? You were taught how to graph in your previous years of studying Mathematics. This lesson will help you deepen your understanding in graphing. This time it’s more of a “level up” stage since you will be graphing polynomial functions with a degree greater than 2. Let’s get started. What Is It In this lesson, you will be provided with illustrative examples and the step- by- step procedure on graphing polynomial functions. Here are some important details that must be kept in mind while graphing polynomial functions. Use graphing paper or notebook when plotting. 1. The graph of a polynomial function is continuous because every polynomial function with real coefficients has the set of real numbers as its domain. Furthermore, it means that there are no holes or gaps in which you can even draw the graph without lifting your pen. Also, the graph of polynomial function is smooth, it has no sharp corner and the turns are rounded. 2. Every polynomial function of the nth degree cannot have more than n roots (Fundamental Theorem of Algebra), which means the graph cannot intersect the x-axis more than n times. 3. A polynomial function of degree n has n-1 turning points on its graph or the number of turning points is always less than n. 4. The multiplicity of root r is the number of times that x-r is a factor of f(x). When a real root has even multiplicity, the graph of f(x) is tangent to the x-axis. When a real root has odd multiplicity greater than 1, the graph bends as it crosses the x-axis. Example 1: Sketch the graph of f(x) = x3 – 2x2 – x + 2 Steps 1. Determine the end behavior of the graph 2. Find the x Expression f(x) = x3 – 2x2 Discussion –x+2 Let f(x)= 0 i. f(x)= x3 – 2x2 – x + 2 21 The leading coefficient is 1 and it is positive, and the degree is 3 and it is an odd number, thus the graph rises to the right and falls to the left. Equate the equation to zero. intercept 3. Find the y intercept 0 = x3 – 2x2 – x + 2 0= (x+1)(x-1)(x-2) x+1=0; x-1=0 & x-2=0 x= -1 x= 1 x=2 (-1,0) (1,0) (2,0) Apply the Zero Product Property to get the xintercepts. Therefore , the graph will pass through (-1,0) (1,0) (2,0). Let x= 0 f(x) = x3 – 2x2 – x + 2 f(x)= (0)3 – 2(0)2 – 0 + 2 f(x)= 0 –0 – 0 + 2 f(x)= 2 (0,2) Substitute x to zero (0) and simplify 4. Sketch the graph The graph will also pass through (0, 2). You may also find other points on the graph by making a table of values. X -3 -2 -1 0 1 2 3 40 -12 0 2 0 0 8 y Notice that your graph of f(x) = x3 – 2x2 – x + 2 crosses the x- axis 3 times, it’s because the degree of your function is 3. A polynomial function of the nth degree cannot have more than n roots. This means that the graph cannot intersect the x-axis more than n times. It is true that the graph falls to the left and rises to the right as we have mentioned in Step 1 using the Leading Coefficient Test. The turning points of a graph occur when the function is changing values, from decreasing to increasing or from increasing to decreasing. A polynomial function of degree n has n-1 turning points on its graph or the number of turning points is always less than the degree n. The graph above illustrates 2 turning points since the degree of f(x) is 3. Sometimes a polynomial functions has a factor that occurs more than once. This makes a multiple root. The multiplicity of root r is the number of times that x-r is a factor of f(x). When a real root has even multiplicity, the graph of f(x) is tangent to the x-axis. When a real root has odd multiplicity greater than 1, the graph bends as it crosses the x-axis. Consider the next example. Example 2:Sketch the graph of y = (x+1)(x+2)2(x-1)3 22 Steps 1. Determine the end behavior of the graph. If you get the product of the polynomials, the leading term will be x6. 2. Find the x intercept. (The given is in factored form already, there’s no need to factor the polynomial completely.) Expression y= Discussion The leading coefficient is 1 and it is positive, the degree is 6 and it is an even number, thus the graph rises to the right and rises to the left. (x+1)(x+2)2(x-1)3 Let y= 0 i. y= (x+1)(x+2)2(x-1)3 0 = (x+1)(x+2)2(x-1)3 (x+1)=0 (x+2)2=0 (x-1)3=0 x+1=0; x= -1 (x+2)2=0 Equate the equation to zero Applying the Zero Product Property. = x- 1= 0 x=1 Equate each factor to zero and simplify = x+2=0 x = -2 (-1,0), (-2,0), (1,0) 3. Find the y intercept Let x= 0 y= (x+1)(x+2)2(x-1)3 y= (0+1)(0+2)2(0-1)3 y= (1)(2)2(-1)3 y=-4 (0,-4) 4. Sketch the graph 23 The graph will pass through (-1,0), (-2,0), (1,0) Equation Substitute x to zero (0) and simplify The graph will also pas through (0,-4) You may also find other points on the graph by making a table of values. X -2 -1 0 1 2 y 0 0 -4 0 48 Notice on the graph where your zero is -2, the given factor is (x+2)2, meaning to say the factor (x+2) occurred twice. When a real root has even multiplicity, the graph of the function is tangent the x-axis, it simply touches it but does not cross the x-axis. This is true for even multiplicity (the exponent is even). Thus -2 is of even multiplicity 2. Observe the graph where the zero is 1 where the given factor is (x-1)3. When a real root has odd multiplicity, the graph bends as it crosses the x-axis, hence 1 is an odd multiplicity 3. Look at this table for more illustration. Roots Multiplicity -2 Even Polynomial functions Leading Term -1 1 End behavior of the graph Odd Odd Behavior of the graph relative to x-axis Is tangent to factors Roots yinterce pts Turning points Crosses Crosses You are now equipped with knowledge on how to sketch the graph of polynomial functions. It’s now your turn to do the next activity. What’s More Here is an activity to help you check your understanding on the lesson. Complete the table below. GUIDED PRACTICE You start with the column with the given so that it would be easy for you to fill out the other parts of the table. 24 y=x4-2x3 -7x2+8x+12 1. 2. 3. 4. 5. 6. 7. 8. 9. (x-2) (x+2) (x-3)(x+3) 10. 11. 12. 13. 14. 15. 16. -2,1,5 17. 18. INDEPENDENT PRACTICE Sketch the graph of the given polynomial functions. 1. y = x4-2x3 -7x2+8x+12 2. y = (x-2) (x+2) (x-3)(x+3 3. y = (x+2)(x-1)(x-5) What I Have Learned In the previous module, you have learned that one of the ways to get the factor of polynomial function is through Division. But what is the mathematical name for the division symbol (÷)? To find put, do the activity below. Match the letter to its corresponding answer and write the letter below. Column A Column B B: a given factor of polynomials with a root of even multiplicity A. y = x3 + 7x2 + 7x – 15 L: a given factor of polynomials with a root of odd multiplicity B. y = (x-2)2(x-1)4 S: polynomial function with 3 turning points C. y = -x5 + 3x4+x3- 7x2+4 O: polynomial function with (x+3) as one of the factor D. f(x) = (x+1)(x-1)3 E. y= x3 + 8x2 +17x +10 E: This graph’s end behavior rises to the left but falls to the right. F. f(x) = -x4+2x3+13x2-14x- U: polynomial function with -2 as one of its roots. 24 25 ____ ____ ____ ____ ____ ____ A B C D E F Thus, the mathematical name of the division symbol is ___________. Well, the activity that you have just answered contains some important details in graphing polynomial functions. It is important that you keep them in your mind so that you can have a broader idea and a bigger picture in your mind on the sketch of your graph What I Can Do Now it’s your turn. For each of the given polynomial function, do the following and sketch the graph. 1. 2. 3. 4. 5. describe the leading term (2 pts) determine the end behaviors (2 pts) find the x-intercepts and y-intercepts (3 pts) create table of values (3 pts) sketch (4 pts) i. y = x4 + 5x3 + 2x2 – 8x ii. y = (x+2) ( 2x+1) (x+3) Have you sketch the graph of the polynomial functions given above? I hope you enjoy doing the activities. The next activities will bring you more items to test your mastery, so keep going! Assessment GUIDED PRACTICE Complete the table below. Polynomial Functions Roots Sketch 26 Turning Points 1. . y = (x-1)(x+1)(x-3)(x-2) 2. y = x3 + 7x2 + 7x – 15 3. y = (x-3)(x-1)(2x-1) INDEPENDENT PRACTICE It’s time to do your own thing. Examine the graph below and answer the question given. Give at least 2 out of 3 different reasons why the graph below cannot be the graph of f(x) = x4 + x2 + 1. 27 Additional Activities Below are set of activities that will help you gain mastery in finding the coordinates on the graph. Sketch the graph of the following polynomial functions with a credit of 3 points each graph. 11. f(x) = x4 + x3 – 5x2 – x +6 12. f(x) = x5 + 2x4 – x3 – 6x2 – 4x 13. f(x) = 2x3 - 5x + 7 14. f(x) = x3 + 8x2 + 20x + 16 15. f(x) = x3 - 5x2 + 6x – 5 Summary The Leading Coefficient Test is a test to determine the end behavior of the graph of polynomial function by describing the leading term. It comes with 4 cases. 1. If the degree of the polynomial is odd and the leading coefficient is positive, then the graph falls to the left and rises to the right. 2. If the degree of the polynomial is odd and the leading coefficient is negative, then the graph rises to the left and falls to the right. 3. If the degree of the polynomial is even and the leading coefficient is positive, then the graph rises to the left and rises to the right. 4. If the degree of the polynomial is even and the leading coefficient is negative, then the graph falls to the left and falls to the right. The graph of a polynomial function is continuous and smooth and has rounded turns. A polynomial function of degree n has n-1 turning points. 28 Every polynomial function of the nth degree cannot have more than n roots. Here are the steps to sketch the graph of a polynomial function 1. Identify the end behavior of the graph through the Leading Coefficient Test. 2. Factor the polynomials completely (if the given is not in factored form) 3. Find the x- intercepts as well as the y-intercepts to determine where on the x and y axis the graph passes through. 4. Plot the other points. A zero has a "multiplicity", which refers to the number of times that its corresponding factor appears in the polynomial. When a real root has even multiplicity, the graph of f(x) is tangent to the x-axis. When a real root has odd multiplicity greater than 1, the graph bends as it crosses the x-axis. 29 POST-TEST Choose the letter of the correct answer. 1. Which of the following graphed function has the negative leading coefficient and an even degree? A B C D 2. What is the factored form of the polynomial function y = x4 + x3 – 7x2 – x + 6 ? A. f(x) = (x-1)(x-2)(x-3)(x-2) C. f(x) = (x+1)(x-2)(x-3)(x+3) B. f(x) = (x+1)(x+2)(x-3)(x-3) D. f(x) = (x+1)(x-2)(x+3)(x-1) 3. If the end behavior of a graph of the polynomial function rises both to the left and to the right, which of the following is true about the leading term and degree? A. the leading coefficient is positive, the degree is odd B. the leading coefficient is positive, the degree is even C. the leading coefficient is negative, the degree is odd D. the leading coefficient is negative, the degree is even 4. What is the y- intercept of the function y = (x+2)(x-2)(x-4) ? A. -16 B. 8 C. 16 D. 32 5. How will you sketch the graph of y = x (x-1)4 with respect to the x-axis? A. sketch it tangent at both (1,0) and (0,0) B. sketch it crossing (1,0) and tangent to (0,0) C. sketch it tangent at (1,0) and crossing (0,0) D. sketch it crossing both (1,0) and (0,0) 6. Give the leading coefficient of the polynomial function y = – 4x2+3x3+ 3x – 2 ? 30 A. -4 B. 2 C. 3 D. 4 7. Which of the following is the graph of y = x3 – 5x2 + 6x – 5? A. B. C. D. 8. Which of the following represents a polynomial function? A. y = B. y = 4/(x+2) +1 C. y = 4x2.5+8x-3+2x+3 D. y = 3x3 – 7x2 +4x – 2 9. Which function could describe the graph? A. f(x) = 2x5 – x2 + 75 B. f(x) = -5x3 + x – 8 C. f(x) = x2 + 5x + 6 D. f(x) = -x4 + 3x3 – 4x + 2 10. How many turning points will a quartic function with four real zeros have? A. 1 B. 2 C. 3 D. 4 11. What is the multiplicity of the root 2 in the equation y = x4-2x3-3x2+4x+4? A. 1 B. 2 C. 3 D. 4 12.Which polynomial function has zeros -2, ½, 2, 1? A. y = 2x4 – 3x3 – 7x2 +12x – 4 B. y = 2x3 – 3x2 – 7x +12 C. y = 3x3 – 7x2 +12x – 4 D. y = 3x4 – 7x2 +12x – 4 13. To define a polynomial function, what should be n if f(x) = xn? A. any real number C. a positive integer B. a negative integer D. any integer 14. Determine whether the given binomial is a factor of the polynomial f(x). A. (x-3); f(x)= x3+2x-3 C. (x+4); f(x) = 2x4+8x3+2x+8 B. (x-2); f(x) = x4-2x3+3x2+4x+4 D. (x+5); f(x) = x4-2x3+3x2+4x+25 15. What is the degree of the polynomial function y = x3 – 4x2 + 3x – 2 ? A. 1 B. 2 C. 3 D. 4 31 Answer Key PRETEST 1. B 2. A 3. C 4. A 5. D 6.A 7.C 8.A 9.D 10.C 11.A 12.A 13.C 14.D 15.D LESSON 1 WHAT I KNOW 1.A 2. B. 3. C 4. D 5. A 6. B 7. D 8. B 9. D 10. A 11. C 12. A 13. C 14. C 15.D WHAT’S IN 1. 3x4 2. 3 3. 4 4. –x4 5. -1 6. 4 7. x3 8. 1 9. 3 10. -2x5 11. -2 12. 5 WHAT’S NEW B. Polynomial function: y= -3x3- 2x2 + 8x Leading term: -3x3 Leading coefficient : -3, negative Degree : -3, odd C. Polynomial functions: y = x4 – 3x2 – 3 Leading term: x4 Leading coefficient : 1, positive Degree : 4, even D. Polynomial Functions: y = -3x2 – 6x + 4 Leading term: -3x2 Leading coefficient : -3, negative Degree : 2, even 32 E. Polynomial functions: f(x) = x3 + 4 Leading term: x3 Leading coefficient : 1, positive Degree : 3, odd WHAT’S MORE GUIDED PRACTICE B. y = -2x3 + x2 + 18x – 9 1. The leading term is -2x3 2. The leading coefficient is -2 and it is negative. 3. The degree is 3 and it is odd. 4. Since the leading coefficient is negative and the degree is od d, then the graph rises to the left and falls to the right. 5. Possible sketch: C. y = 4x3 – 4x2 – 19x +10 1. The leading term is 4x3 2. The leading coefficient is 4 and it is positive. 3. The degree is 3 and it is odd. 4. Since the leading coefficient is positive and the degree is odd, then the graph falls to the left and rises_ to the right. 5. Possible sketch: D. y = x4 – 10x2 + 9 1. The leading term is x4 2. The leading coefficient is 1 and it is positive. 3. The degree is 4 and it is even. 4. Since the leading coefficient is positive and the degree is even_, then the graph rises to the left and rises to the right. 5. Possible sketch: Possible Sketch B,C,D, INDEPENDENT PRACTICE: 1. 2. 3. 4. 5. 6. 7. 8. Negative Negative Positive Negative Odd Odd Even Odd 33 WHAT I HAVE LEARNED Polynomial Functions f(x) = 3x3 – 8x2 -8x +8 f(x) = -x4 - 6x3+9x2-6x+8 f(x) = -x3 – 4x2 + x+ 6 Leading Coefficient (positive/negative) 1. positive 2. negative 3. negative Degree (odd/even) 4. odd 5.even 6.odd Behavior of the Graph Left side 7.falling 8. falling 9. rising Right side 10. rising 11. falling 12. falling WHAT I CAN DO Amihan shows the graph correctly because it follows the Leading Coefficient Test. From the function, the leading coefficient is positive and the degree is even, therefore the end behavior of the graph on the left side is rising as well as on the right side and Amihan shows the graph correctly. ASSESSMENT: GUDED PRACTICE 1. negative 2. Even 3. Falls to the left, falls to the right 4. positive 5. Even 6. Rises to the left , rises to the right 7. negative 8.odd 9. Rises to the left, falls to the right 10. positive 11. Odd 12. Falls to the left, rises to the right 13. positive 14. Even 15. Rises to the left, rises to the right INDEPENDENT PRACTICE 1. negative leading coefficient – odd degree 2. Negative leading coefficient – even degree 3. positive leading coefficient – even degree 4. Negative leading coefficient- even degree 5. negative leading coefficient – even degree 6. Positive leading coefficient – odd degree 7. negative leading coefficient – even degree 8. Negative leading coefficient – odd degree 9. negative leading coefficient – even degree 10. Negative leading coefficient – odd degree 11. negative leading coefficient – odd degree 12. Negative leading coefficient – odd degree 13. positive leading coefficient – even degree 14. Positive leading coefficient – odd degree 15. positive leading coefficient – even degree 34 ADDITIONAL ACTIVITIES 1. f(x) = 2x6 + 3x4 + 5x2 2. f(x) = -5x3 + x – 8 3. f(x) = -4x2 + 3x – 1 4. f(x) = 2x6 + 3x4 + 5x2 5. f(x) = 5x3 + 9x + 1 6. f(x) = 5x3 + 9x + 1 7. f(x) = -4x2 + 3x – 1 8. f(x) = -5x3 + x – 8 9. f(x) = 3x6 + 4x5 - 2x + 4 10.f(x) = -x5 + 5x4 + 1 11. f(x) = -3x4 – 8x2 + 5 12. f(x) = 3x6 + 4x5 - 2x + 4 13. f(x) = 2x3 +3x2 – 4x 14. f(x) = 2x3 +3x2 – 4x 15.f(x) = 2x3 +3x2 – 4x 16. f(x) = -x5 + 5x4 + 1 LESSON 2 WHAT I KNOW 1. A 2. C 3. A 4. B 5. D 6. D 7. C 8. A 9. B 10. C 11. A 12. B 13. D 14. C 15. A WHAT’S IN Polynomial Function Factors Roots 7x2 – y=(x+3)(x-2)(x+1)(x-1) -3,2,-1,1 y = (x+5)(x-5)(x-1) 5, -5, 1 y= (x+4)(x+4)(x-3)(x-1) -4 (2 times), 3,1 y= (x(x-3)(x+3)(x+6 0, 3, -3, -6 y = x(x-9)(x+1)(x-1) 0, 9, 1, -1 1. y = x4 + x3 - 2. y = x3 + 9x2 + 3. y = x4 4x3 + – x+6 15x – 25 13x2 -40x + 48 4. y = x4 + 6x3 – 9x2 - 54x 5. y = x4 – 9x3 –x2 + 9x 35 WHAT’S NEW Here is the graph of f(x) = x2 and f(x) =x3 WHAT’S MORE GUIDED PRACTICE y = x4 – 2x3 – 7x2 + 8x + 12 1. x4 2. rises to the left, rises to the right 3.(x+1)(x-3)(x-2)(x+2) 4. -1, 3, 2, -2 5. 12 6. 3 7. y = x4 – 13x2 + 36 8. x4 9. rises to the left, rises to the right 10. 2, -2, 3, -3 11. 36 12. 3 13. y = x3 – 4x2 – 7x + 10 14. x3 15. falls to the left, rises to the right 16. (x+2)(x-1)(x-5) 17. 10 18. 2 36 INDEPENDENT PRACTICE 1. y = x4 + x3 – 7x2 –x + 6 1. y = (2x+3)(x-2)(x-1) 1. y = x3 – 4x2 – 7x + 10 WHAT I HAVE LEARNED OBELUS – the mathematical name of the division symbol. 37 WHAT I CAN DO y = x4 + 5x3 + 2x2 – 8x 1. The leading coefficient is positive and the degree is odd 2. The end-behavior of the graph is rising on both sides. 3. x-intercepts -4, -2, 0, 1 y-intercept 0 4. i. X -4 -3 -2 -1 0 1 2 3 y 0 -12 0 6 0 0 48 210 5. 38 ii. 1. The leading coefficient is positive and the degree is odd 2. The end behavior of the graph on the left side is falling while rising on the right side 3. x-intercepts -2, -1/2, -3 y-intercept 6 4. X -4 -3 -2 -1 0 1 2 3 y -14 0 0 -2 6 36 100 210 5. LESSON 2: ASSESSMENT GUIDED PRACTICE 1. Roots: 1, -1, 3, 2 Turning Points: 3 2. Roots: -5, -3, 1, Turning Points: 2 3. Roots: 3, 1, 1/2, Turning Points: 3 39 INDEPENDENT PRACTICE Give at least 2 out of 4 different reasons why the graph below cannot be the graph of f(x) = x4 + x2 + 1 1. 2. 3. The given polynomial has degree 4 and positive leading coefficient , hence the graph should rise on the left and on the right side. y- intercept is 1but the graph shows that it did not pass through (0,1) The equation has no solution which suggests that the function f(x) = x4 + x2 + 1 has no zeros, yet the graph shows x – intercepts. INDEPENDENT PRACTICE 1. 3. 2. 4. 5. POST TEST 1. A 2. D 11. B 12. A 3. B 13. C 4. C 14. C 5. C 15. C 6. C 40 7. A 8. D 9. D 10. C References BURGER, EDWARD, CHARD, DAVID, ET AL. Algebra 2, United States of America, 2007 CALLANTA, MELVIN, CANONIGO, ALLAN, ET AL. Mathematics 10 Learner’s Module, Rex Book Store Inc., Sampaloc, Manila, Philippines, 2015. DILAO, SOLEDAD, ORINES, FERNANDO, ET AL. Advanced Algebra, Trigonometry and Statistics(Revised Edition) , SD Publications, Inc., Quezon City, Philippines 2009. ORONCE, ORLANDO AND MENDOZA, MARILYN. 2007. E-Math IV(First Edition), Rex Book Store Inc., Sampaloc, Manila, Philippines, 2007 DESMOS graphing calculator : https://www.desmos.com/calculator Microsoft Mathematics Software https://www.wtamu.edu/academic/anns/mps/math/mathlab/col_algebra/col_al g_tut35_polyfun.htm Lesson Tutorial Videos: https://www.youtube.com/watch?v=CHEtGgTexHI https://www.youtube.com/watch?v=3ANqMj5cfY8 For inquiries and feedback, please write or call: Department of Education –Learning Resources Management and Development Center (LRMDC) DepEd Division of Bukidnon Sumpong, Malaybalay City, Bukidnon Telefax: ((08822)855-0048 E-mail Address: bukidnon@deped.gov.ph 41