1. Write and Graph Equations of Lines
Section 3 – 5
Write and Graph Equations of Lines

2. Vocabulary
Slope-intercept form:
y = mx +b
m = slope b = y-intercept

3. Vocabulary Standard Form: Ax + By = C
x-intercept: The x-coordinate of a point where a graph crosses the x-axis.
y-intercept: The y-coordinate of a point where a graph crosses the y-axis.

4. Example 1
Write the equation of the line in slope-intercept form.
m = 4 1
= 4
b = -3 x
y = 4x – 3 y

5. Example 2 Step 1: What is the slope of the given line? 6
Write an equation of the line passing through the point (2, -3) that is parallel to the line y = 6x + 4.
Step 1: What is the slope of the given line? 6
Step 2: Put the given point and the slope into slope-intercept form to solve for b.
Step 3: Take the slope & y-intercept and write the new equation.
y = mx + b
-3 = 6(2) + b
-3 = 12 + b
y = 6x – 15
b = -15

6. Example 3 Step 1: What is the slope of the given line? -½
Write an equation of the line passing through the point (3, -4) that is perpendicular to the line y = -½x – 1.
Step 1: What is the slope of the given line? -½
Step 2: Find the opposite reciprocal: 2
Step 3: Put the given point and the new slope into slope-intercept form to solve for b.
y = mx + b
-4 = 2(3) + b
Step 4: Take the slope & y-intercept and write the new equation.
-4 = 6 + b
b = -10
y = 2x – 10

7. Homework Section 3-5 Page 184 – 187 3 – 6, 9, 10 – 20 even,
22 – 24, 27, 29,
32, 33