Download PROP Lesson 25 Luke

Write linear equations from tables or graphs.
Use the table below to answer the following questions.
Does the graph model direct variation?
What is the slope?
Write an equation for the graph.
x
-2
-1
0
1
2
y
-6
-3
0
3
6

Linear Functions:
A function whose graph is a line.
Y-intercept:
Where the line crosses the y-axis
b is the symbol for the y-intercept

What # are you counting by for the y-values?

What is y when x = 0 ?
◦ This is b …
 where the line crosses the y-axis …
 y-intercept


y = b plus or minus the slope times x
y = b ± mx

Find b
(0,??)
y-intercept is where the line crosses the y-axis

Find slope
y/x
the # are you counting by for the y values
rise over run

Y = ?? ± slope times x
y = b ± mx
Find the linear equation for the input-output table.


Start Value is
paired with 0.
Start value is 11.
y = 11 ± ____x

Find difference
in the outputs.

Rate of change
is the difference: – 3

Finish the equation.
y = 11 – 3x
Find the linear equation for
the graph.

Create an input-output
table from each point.


Find start value: – 4
y = – 4 ± ____x

Find rate of change: +2

Finish the equation.
y = – 4 + 2x
1.
2.
Find the linear equation for the
input-output table.
Use the equation y = –5 + x.
Input
x
-1
0
1
2
3
Output
y
5
3
1
-1
-3
a) What is the rate of change?
b) What is the start value?
c) Is the graph of this function a) increasing or b) decreasing?
How do you know?
How is a direct variation equation a special type of linear
equation?
Lesson 25
Writing Linear Equations
1.
Given a linear graph, create an input-output table using the
ordered pairs of the points on the graph.
2.
Determine the start value (the output number paired with an
input of zero).
3.
Determine the rate of change (the amount the output number
increases or decreases when the x-value increases by one unit).
4.
Write the equation by filling in the start value, operation and
rate of change:
y = __ ± __ x