1. Substitute either point and the slope into the slope-intercept form.
Example 1
Write the equation of the line that passes through (3, –4) and (–1, 4) in slope-intercept form.
Find the slope. =
y2 – y1
x2 – x1
4 – (–4)
–1 – 3 8 –4 =
= –2
The slope is –2.
Substitute either point and the slope into the slope-intercept form.
y = mx + b
Substitute –1 for x, 4 for y, and –2 for m.
4 = –2(–1) + b
4 = 2 + b
Simplify.
Course 3

2. Subtract 2 from both sides.
Example 1 Continued
Solve for b.
4 = 2 + b
–2 –2
Subtract 2 from both sides.
2 = b
Write the equation of the line, using –2 for m and 2 for b.
y = –2x + 2
Course 3

3. Substitute either point and the slope into the slope-intercept form.
Example 2
Write the equation of the line that passes through (1, 2) and (2, 6) in slope-intercept form.
Find the slope. =
y2 – y1
x2 – x1
6 – 2
2 – 1 4 1 =
= 4
The slope is 4.
Substitute either point and the slope into the slope-intercept form.
y = mx + b
Substitute 1 for x, 2 for y, and 4 for m.
2 = 4(1) + b
2 = 4 + b
Simplify.
Course 3

4. Using Slopes and Intercepts
Course 3
Using Slopes and Intercepts
Example 2 Continued
Solve for b.
2 = 4 + b
–4 –4
Subtract 4 from both sides.
–2 = b
Write the equation of the line, using 4 for m and –2 for b.
y = 4x – 2