February 10, 2015
4-2: Graphing Linear Functions
Outcome:
• To use tables and equations to graph linear functions
The y-intercept is the point
where the graph crosses the yaxis.
slope-intercept form:y = mx + b
y = ___x + ___
A linear function is a function with points that lie on a line.
February 10, 2015
Finding the Slope and y-intercept ...
Find the slope and y-intercept of the graph of the function.
A. y = 2x + 4
B. y = -5/6x - 7
C. y = x - 3
D. y = -4x + 3
More than One Way ...
Graph the function y = 3/5x + 1
x
0
1
2
3
4
y
OR ...
February 10, 2015
Graph the function y = 3/5x + 1 by plotting the y-intercept,
and then applying the slope to it!
Below is the graph of y = 2x.
Notice that the slope of the
line is 2, or 2/1 and the yintercept is the origin, or 0.
So the equation of the slopeintercept form is y = 2x + 0 or
y = 2x.
February 10, 2015
The temperature of a substance in degrees Celcius before and
during an experiment is given by the function y = -4/5x where y
represents temperature and x represents time in minutes.
Graph y = -4/5x
4-3: Writing Rules for Linear
Functions
Outcome:
• To write function rules from words, tables, and graphs
February 10, 2015
Writing a Fuction Rule from Words ...
A toll-free telephone number is $2.95 per month plus $0.10 per
minute. Which function rule represents the monthly cost?
A. y = 0.1 + 2.95x
C. y = 2.95 - 0.1x
B. y = 2.95 + 0.1x
D. y = 0.1x - 2.95
Quick Check:
An orchestra buys music stands for $42 each with $298 in its
bank account. Write a function rule that shows how the account
balance depends on the number of stands bought. What are the
initial value and rate of change of the function.
February 10, 2015
Writing a Rule From a Table ...
The table compares how the water level of a lake over time compares to its average
water level. Write a function rule. What are the initial value and rate of change?
Number of
Days, x
0
2
4
6
10
7
4
1
Water
Level
Compared
to Average,
y
Writing a Rule From a Graph ...
Malik is a car salesman. He earns a base salary and a commission for each car he
sells. The graph shows this relationship. Write a function rule. What is Malik's
Amount Earned ($$)
base salary? How much does he earn in commission for each car he sells?
25,000
20,000
15,000
10,000
5,000
0
10
20
Number of Cars Sold
February 10, 2015