Chapter 1: Linear
Relations and Functions
Section 1-4:
Writing Linear Equations
Objectives
Learn how to translate English words into
mathematical words to solve a problem.
A mathematical model
In real life situations we use equations to
help us solve problems. Often when you
work with real life data, you can use
characteristics of the graph of the data to
write an equation of the line. This equation
is the model of the data and can help you
find out more information about the
information.
Example
Ms. Rodrigues is preparing her college math
classroom for a new year of school. She
placed a purchase order for $285 to buy a
computer workstation for the clasroom. In
addition, she expects the expenses each
month for technology supplies to be about
$120. Write an equation that models the
total expense y after x months.
Y = 120x + 285
Point-Slope Form of an equation
If the point with coordinates ( x1 , y1 ) lies on a line
having slope m, the point-slope form of the
equation of the line can be written as follows:
y-y1=m(x-x1)
Assessment
1. Compare and Contrast: On a piece of paper compare and contrast the slope-intercept
and point-slope forms of linear equations. Also name situations for which one form is
preferable to the other.
2. What are the domain and range of the relation Is the relation a function? Explain.
(-2,3), (-2,-3),(4,7), (2,-8)
3. Find f(4) for f (x) = 7 − x
4. If
2
1
x −1
and g(x) = x + 1,
3
,
x −1
what is g ( n + 2)
If
g ( x) =
5.
f ( x) =
[ ] ( x)
[ ] ( x)
find f o g
and g o f
6. Find the zero of f (x) = 5x -3 and graph the equation
7. Points A (2,5) and B (7,8) lie on line W. What is the standard for of the equation of line
W?
8. In July 1990, the population of Georgia was 6,506,416. By July 1997, the population had
grown to 7,486,242.
a. If x represents the year and y represents
the population, find the average annual rate
of increase of the population.
b. Write an equation to model the population change.
HW #4
Section 1-4
PP. 30-31
#11, 12, 13, 15, 17, 20, 30, 31,
33, 34, 35
Study for quiz over sections 1:1-1:4