1. Use slope and y-intercept to write an equation
EXAMPLE 1
Use slope and y-intercept to write an equation
Write an equation of the line with a slope of –2 and a y-intercept of 5.
y = mx + b
Write slope-intercept form.
y = –2x + 5
Substitute –2 for m and 5 for b.

2. Standardized Test Practice
EXAMPLE 2
Standardized Test Practice
Which equation represents the line shown? A
y = – x + 3 2 5 B C
y = – x + 1 D
y = 3x + = –
The slope of the line is
rise
run –2 5 2 .
The line crosses the y-axis at (0, 3). So, the y-intercept is 3.
y = mx + b
Write slope-intercept form. 2
y = – x + 3 5 2
Substitute – for m and 3 for b. 5

3. EXAMPLE 2
Standardized Test Practice
ANSWER
The correct answer is A. B D C A

4. GUIDED PRACTICE
for Examples 1 and 2
Write an equation of the line with the given slope and y-intercept.
1. Slope is 8; y-intercept is –7.
y = 8x – 7
ANSWER

5. GUIDED PRACTICE
for Examples 1 and 2
Write an equation of the line with the given slope and y-intercept.
2. Slope is ; y intercept is –3. 3 4
y = 3 4
x – 3
ANSWER