Warm Up
Find the value of each expression.
1.
25
2.
2–5
3.
–34
5.
(0.2)3
6.
7(–4)2
7.
15 ( )
1 3
3
4.
(–3)4
8.
12(–0.4)3
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Algebra/Lesson 9-1: Geometric Sequences
Objectives:


Recognize and extend geometric sequences.
Find the nth term of a geometric sequence.
The table shows the heights of a bungee jumper’s bounces.
The height of the bounces shown in the table above form a geometric sequence. In a geometric sequence, the ratio of successive
terms is the same number r, called the common ratio.
Geometric sequences can be thought of as functions. The term number, or position in the sequence, is the input, and the term itself is
the output.
To find a term in a geometric sequence, multiply the previous term by r.
1
Example 1: Find the next three terms in the geometric sequence.
A.
1, 4, 16, 64,…
B.
C.I.O.-Example 1: Find the next three terms in the geometric sequence.
1a.
5, –10, 20,–40,…
1b.
512, 384, 288,…
To find the output an of a geometric sequence when n is a large number, you need an equation, or function rule.
The pattern in the
table shows that to get
the nth term, multiply
the first term by the
common ratio raised
to the power n – 1.
2
Example 2: Finding the nth Term of a Geometric Sequence
2A.
2C.
The first term of a geometric sequence is 500, and
the common ratio is 0.2. What is the 7th term of
the sequence?
2B.
For a geometric sequence, a1 = 5, and r = 2. Find the
6th term of the sequence.
What is the 9th term of the geometric sequence
2, –6, 18, –54, …?
C.I.O.-Example 2:
What is the 8th term of the sequence 1000, 500, 250, 125, …?
3
Example 3: Solve each system by elimination.
A ball is dropped from a tower. The table shows the heights of the balls bounces, which form a geometric sequence. What is the height
of the 6th bounce?
C.I.O.-Example 3:
The table shows a car’s value for 3 years after it is purchased. The values form a geometric sequence. How much will the car be worth
in the 10th year?
4
Lesson Quiz: Part I
Find the next three terms in each geometric sequence.
1.
3, 15, 75, 375,…
2.
3. The first term of a geometric sequence is 300 and the common ratio is 0.6. What is the 7th term of the sequence?
4. What is the 15th term of the sequence 4, –8, 16, –32, 64…?
Lesson Quiz: Part II
Find the next three terms in each geometric sequence.
5.
The table shows a car’s value for three years after it is purchased. The values form
a geometric sequence. How much will the car be worth after 8 years?
5
Warm Up
Simplify each expression. Round to the nearest whole number if necessary.
1.
32
2.
54
5.
–5(2)5
6.
– (4)3
1
2
3.
2(3)3
4.
7.
100(0.5)2
8.
𝟐
𝟑
(3)4
3000(0.95)8
==========================================================================================
Algebra/Lesson 9-2: Exponential Functions
Objectives:


Evaluate exponential functions.
Identify and graph exponential functions.
The table and the graph show an insect population that increases over time.
A function rule that describes the pattern above is f(x) = 2(3)x. This type of function, in which the independent variable appears in an
exponent, is an exponential function. Notice that 2 is the starting population and 3 is the amount by which the population is
multiplied each day.
6
Example 1:
A.
The function f(x) = 500(1.035)x models the amount of
money in a certificate of deposit after x years. How
much money will there be in 6 years?
B.
The function f(x) = 200,000(0.98)x, where x is the
time in years, models the population of a city. What
will the population be in 7 years?
C.I.O.-Example 1:
The function f(x) = 8(0.75)X models the width of a photograph in inches after it has been reduced by 25% x times. What is the width of
the photograph after it has been reduced 3 times?
Remember that linear functions have constant
first differences and quadratic functions have
constant second differences. Exponential
functions do not have constant differences, but
they do have constant ratios.
As the x-values increase by a constant amount, the y-values are multiplied by a constant amount.
This amount is the constant ratio and is the value of b in f(x) = abx.
7
Example 2: Tell whether each set of ordered pairs satisfies an exponential function. Explain your answer.
2A.
{(0, 4), (1, 12), (2, 36), (3, 108)}
2B.
{(–1, –64), (0, 0), (1, 64), (2, 128)}
This is an exponential
function. As the x-values
increase by a constant
amount, the y-values are
multiplied by a constant
amount.
This is not an exponential
function. As the x-values
increase by a constant
amount, the y-values are
not multiplied by a
constant amount.
C.I.O.-Example 2: Tell whether each set of ordered pairs satisfies an exponential function. Explain your answer.
1a.
{(–1, 1), (0, 0), (1, 1), (2, 4)}
2b.
{(–2, 4), (–1 , 2), (0, 1), (1, 0.5)}
To graph an exponential function, choose several values of x (positive, negative, and 0) and generate ordered pairs. Plot the points and
connect them with a smooth curve.
Example 3:
Graph y = 0.5(2)x.
8
C.I.O.-Example 3:
3a.
Graph y = 2x.
3b.
Graph y = 0.2(5)x.
Example 4:
9
C.I.O.-Example 4:
4a.
Graph y = –6x.
4b.
Graph y = –3(3)x.
Example 5: Graph each exponential function.
5A.
5B.
y = 4(0.6)x
10
C.I.O.-Example 5:
5A.
5B.
y = –2(0.1)x
The box summarizes the general shapes of exponential function graphs.
11
Lesson Quiz: Part I
Tell whether each set of ordered pairs satisfies an exponential function. Explain your answer.
1.
{(0, 0), (1, –2), (2, –16), (3, –54)}
2.
{(0,–5), (1, –2.5), (2, –1.25), (3, –0.625)}
Lesson Quiz: Part II
3.
Graph y = –0.5(3)x.
Lesson Quiz: Part II
4. The function y = 11.6(1.009)x models residential energy consumption in quadrillion Btu where x is the number of years after 2003.
What will residential energy consumption be in 2013?
12
Warm Up
Simplify each expression.
1.
(4 + 0.05)2
2.
25(1 + 0.02)3
3.
1+
0.03
4
4. The first term of a geometric sequence is 3 and the common ratio is 2. What is the 5th term of the sequence?
5. The function f(x) = 2(4)x models an insect population after x days. What is the population after 3 days?
==========================================================================================
Algebra/Lesson 9-3: Exponential Growth and Decay
Objectives:

Solve problems involving exponential growth and decay.
Exponential growth occurs when an quantity increases by the same rate r in each period t. When this happens, the value of the
quantity at any given time can be calculated as a function of the rate and the original amount.
13
Example 1:
The original value of a painting is $9,000 and the value increases by 7% each year. Write an exponential growth function to model this
situation. Then find the painting’s value in 15 years.
C.I.O.-Example 1:
A sculpture is increasing in value at a rate of 8% per year, and its value in 2000 was $1200. Write an exponential growth function to
model this situation. Then find the sculpture’s value in 2006.
A common application of exponential growth is compound interest. Recall that simple interest is earned or paid only on the principal.
Compound interest is interest earned or paid on both the principal and previously earned interest.
14
Example 2:
Write a compound interest function to model each situation. Then find the balance after the given number of years.
2A.
$1200 invested at a rate of 2% compounded quarterly; 3 years.
2B.
$15,000 invested at a rate of 4.8% compounded monthly; 2 years.
C.I.O.-Example 2:
Write a compound interest function to model each situation. Then find the balance after the given number of years.
1a.
$1200 invested at a rate of 3.5% compounded quarterly; 4 years
2b.
$4000 invested at a rate of 3% compounded monthly; 8 years
15
Exponential decay occurs when a quantity decreases by the same rate r in each time period t. Just like exponential growth, the value
of the quantity at any given time can be calculated by using the rate and the original amount.
Notice an important difference between exponential growth functions and exponential decay functions. For exponential growth, the
value inside the parentheses will be greater than 1 because r is added to 1. For exponential decay, the value inside the parentheses will
be less than 1 because r is subtracted from 1.
Example 3:
The population of a town is decreasing at a rate of 3% per year. In 2000 there were 1700 people. Write an exponential decay function
to model this situation. Then find the population in 2012.
C.I.O.-Example 3:
The fish population in a local stream is decreasing at a rate of 3% per year. The original population was 48,000. Write an exponential
decay function to model this situation. Then find the population after 7 years.
16
A common application of exponential decay is half-life. The half-life of a substance is the time it takes for one-half of the substance to
decay into another substance.
Example 4:
Astatine-218 has a half-life of 2 seconds.
4A. Find the amount left from a 500 gram sample of astatine-218
after 10 seconds.
4B. Find the amount left from a 500-gram sample of
astatine-218 after 1 minute.
C.I.O.-Example 4:
4a. Cesium-137 has a half-life of 30 years. Find the amount of cesium-137 left from a 100 milligram sample after 180 years.
4b. Bismuth-210 has a half-life of 5 days. Find the amount of bismuth-210 left from a 100-gram sample after 5 weeks. (Hint: Change
5 weeks to days.)
17
Lesson Quiz: Part I
Write a compound interest function to model each situation. Then find the balance after the given number of years.
1. The number of employees at a certain company is 1440 and is increasing at a rate of 1.5% per year. Write an exponential growth
function to model this situation. Then find the number of employees in the company after 9 years.
2. $12,000 invested at a rate of 6% compounded quarterly; 15 years
Lesson Quiz: Part II
3. $500 invested at a rate of 2.5% compounded annually; 10 years
4. The deer population of a game preserve is decreasing by 2% per year. The original population was 1850. Write an exponential
decay function to model the situation. Then find the population after 4 years.
5. Iodine-131 has a half-life of about 8 days. Find the amount left from a 30-gram sample of iodine-131 after 40 days.
18
Warm Up
1. Find the slope and y-intercept of the line that passes through (4, 20) and (20, 24).
The population of a town is decreasing at a rate of 1.8% per year. In 1990, there were 4600 people.
2. Write an exponential decay function to model this situation.
3. Find the population in 2010.
==========================================================================================
Algebra/Lesson 9-4: Linear, Quadratic, and Exponential Models
Objectives:


Compare linear, quadratic, and exponential models.
Given a set of data, decide which type of function models the data and write an equation to describe the function.
Look at the tables and graphs below. The data show
three ways you have learned that variable quantities can
be related. The relationship shown is linear.
Look at the tables and graphs below. The data show
three ways you have learned that variable quantities can
be related. The relationship shown is quadratic.
Look at the tables and graphs below. The data show three ways you have
learned that variable quantities can be related. The relationship shown is
exponential.
19
In the real world, people often gather data and then must decide what kind of relationship (if any) they think best describes their data.
Example 1: Graph each data set. Which kind of model best describes the data?
1A.
1B.
The data appear to be exponential.
The data appears to be linear.
C.I.O.-Example 1: Graph each set of data. Which kind of model best describes the data?
1a.
1b.
20
Another way to decide which kind of relationship (if any) best describes a data set is to use patterns.
Example 2: Look for a pattern in each data set to determine which kind of model best describes the data.
2A.
2B.
For every constant change in time of +1 second,
there is a constant second difference of –32.
For every constant change in time of + 1 year there is an
approximate constant ratio of 1.17.
The data appear to be quadratic.
The data appears to be exponential.
C.I.O.-Example 2:
Look for a pattern in the data set {(–2, 10), (–1, 1), (0, –2), (1, 1), (2, 10)} to determine which kind of model best describes the data.
After deciding which model best fits the data, you can write a function. Recall the general forms of linear, quadratic, and exponential
functions.
21
Example 3:
Use the data in the table to describe how the number of people changes. Then write a function that models the data. Use your function
to predict the number of people who received the e-mail after one week.
22
C.I.O.-Example 3:
Use the data in the table to describe how the oven temperature is changing. Then write a function that models the data. Use your
function to predict the temperature after 1 hour.
23
Lesson Quiz: Part I
Which kind of model best describes each set of data?
1.
2.
Lesson Quiz: Part II
3. Use the data in the table to describe how the amount of water is changing. Then write a function that models the data. Use your
function to predict the amount of water in the pool after 3 hours.
24
Warm Up
Find the slope of the line that contains each pair of points.
1.
(4, 8) and (-2, -10)
2.
(-1, 5) and (6, -2)
4.
{(-2, 11), (-1, 9), (0, 7), (1, 5), (2, 3)}
Tell whether each function could be quadratic. Explain.
3.
{(-1, -3), (0, 0), (1, 3), (2, 12)}
==========================================================================================
Algebra/Lesson 9-5: Comparing Functions
Objectives:

Compare functions in different representations. Estimate and compare rates of change.
You have studied different types of functions and how they can be represented as equations, graphs, and tables. Below is a review of
three types of functions and some of their key properties.
25
Example 1: Graph each data set. Which kind of model best describes the data?
Sonia and Jackie each bake and sell cookies after school, and they each charge a delivery fee. The revenue for the sales of various
numbers of cookies is shown. Compare the girls’ prices by finding and interpreting the slopes and y-intercepts.
The slope of Sonia’s revenue is 0.25 and the slope of Jackie’s revenue is 0.30.
This means that Jackie charges more per cookie ($0.30) than Sonia does ($0.25).
Jackie’s delivery fee ($2.00) is less than Sonia’s delivery fee ($5.00).
C.I.O.-Example 1:
Dave and Arturo each deposit money into their checking accounts weekly. Their account information for the past several weeks is
shown. Compare the accounts by finding and interpreting slopes and y-intercepts.
26
Remember that nonlinear functions do not have a constant rate
of change. One way to compare two nonlinear functions is to
calculate their average rates of change over a certain interval.
For a function f(x) whose graph contains the points (x1, y1) and
(x2, y2), the average rate of change over the interval [x1, x2] is the
slope of the line through (x1, y1) and (x2, y2).
Example 2:
An investment analyst offers two different investment options for her customers. Compare the investments by finding and interpreting
the average rates of change from year 0 to year 10.
Calculate the average rates of change over [0, 10] by using the points whose x-coordinates are 0 and 10.
27
C.I.O.-Example 2:
Compare the same investments’ average rates of change from year 10 to year 25.
Example 3:
Compare the functions y1 = 0.35x2 - 3x + 1 and y2 = 0.3x2 - 2x + 2 by finding minimums, x-intercepts, and average rates of change
over the x-interval [0, 10].
C.I.O.-Example 3:
Students in an engineering class were given an assignment to design a parabola-shaped bridge. Suppose Rosetta uses y = –0.01x2 +
1.1x and Marco uses the plan below. Compare the two models over the interval [0, 20].
28
Lesson Quiz: Part I
1. Find the average rates of change over the interval [2, 5] for the functions shown.
Lesson Quiz: Part II
2. Compare y = x2 and y = -x2 by finding minimums/maximums, x-intercepts, and average rates of change over the interval [0, 2].
29