1. Writing Linear Equations From Key Information
Lesson 18
Linear Equations
Writing Linear Equations From Key Information

2. Warm-Up Graph each linear equation. Clearly mark at least
three points on each line.
y = −2x

3. Writing Linear Equations From Key Information
Target:
Write a linear equation in slope-intercept form
when given information about the line.

4. Example 1 Write the equation of a line that has a slope of −2 and a
y-intercept of 5.
General Equation: y = mx + b
Slope: m = −2
y-intercept: b = 5
Equation: y = −2x + 5

5. Writing a Linear Equation when Given Key Information
Find the slope (m) of the line.
Find the y-intercept (b) of the line. If necessary, substitute the slope for m and one ordered pair (x, y) for the corresponding variables in the equation y = mx + b. Solve for b.
Write the equation in the form y = mx + b.

6. Example 2
Write the equation of a line that has a slope of and goes through the point (−3, 1).
Write the equation with the slope: y = x + b
Substitute (−3, 1) for x and y in the equation. Solve for b.
1 = (−3) + b
1 = −4 + b
5 = b y-intercept = 5
Equation: y = x + 5

8. Exit Problems Write the equation of each line in slope-intercept form.
slope = 4 y-intercept = −5
slope = goes through (2, 6)
goes through (0, 4) and (−2, 8)

9. Communication Prompt
How do you find the equation of a line when you are
given two points the line passes through?