Download Write Linear Equations in Slope-Intercept Form

5.1
Write Linear Equations in
Slope-Intercept Form
Goal
Your Notes
Use the slopeintercept form
(y 5 mx 1 b) to
write an equation
of a line if slope
and y-intercept are
given.
p Write equations of lines.
Use slope and y-intercept to write an equation
Example 1
Write an equation of the line with a slope of 24 and a
y-intercept of 6.
Solution
y 5 mx 1 b
y5
x1
Write slope-intercept form.
Substitute
for b.
for m and
Checkpoint Write an equation of the line with the
given slope and y-intercept.
1. Slope is 8;
y-intercept is 25.
3. Slope is 23;
y-intercept is 7.
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2
;
2. Slope is }
3
y-intercept is 22.
5
4. Slope is 2}
;
2
y-intercept is 9.
Lesson 5.1 • Algebra 1 Notetaking Guide
119
Your Notes
Example 2
Write an equation of a line given two points
Write an equation of the line shown.
Solution
Step 1 Calculate the slope.
y
(0, 4)
y 2y
x2 2 x1
2
1
m5}
You can write an
equation of a line
if you know the
y-intercept and any
other point on the
line.
3
1
5
2
1
21
21
23
2
(3, 22)
23
5
x
3
5
Step 2 Write an equation of the line. The line crosses the
y-axis at
. So, the y-intercept is
.
y 5 mx 1 b
y5
x1
Write slope-intercept form.
Substitute
for b.
for m and
Checkpoint Complete the following exercise.
5. Write an equation of the line shown.
1
21
21
23
y
3
1
5
x
(5, 23)
25
(0, 26)
120
Lesson 5.1 • Algebra 1 Notetaking Guide
Copyright © Holt McDougal. All rights reserved.
Your Notes
Example 3
Write a linear function
Write an equation for the linear function f with the
values f(0) 5 4 and f(2) 5 12.
Solution
Step 1 Write f(0) 5 4 as
.
and f(2) 5 12 as
Step 2 Calculate the slope of the line that passes
through
and
.
y 2y
x2 2 x1
2
1
m5}
5
2
2
5
5
Step 3 Write an equation of the line. The line crosses the
y-axis at (0,
). So, the y-intercept is
.
y 5 mx 1 b
Write slope-intercept form.
y5
Substitute
for b.
The function is
for m and
.
Checkpoint Complete the following exercise.
Homework
6. Write an equation for the linear function with the
values f(0) 5 3 and f(3) 5 15.
Copyright © Holt McDougal. All rights reserved.
Lesson 5.1 • Algebra 1 Notetaking Guide
121