1. EXAMPLE 2 Find a negative slope Find the slope of the line shown. m = y 2 – y 1 x 2 – x 1 Let (x 1, y 1 ) = (3, 5) and (x 2, y 2 ) = (6, –1). –1 – 5 6 – 3 = – 6 3 = = –2–2 Write formula for slope. Substitute. Simplify.

2. EXAMPLE 3 Find the slope of a horizontal line Find the slope of the line shown. Let (x 1, y 1 ) = (–2, 4) and (x 2, y 2 ) = (4, 4). m = y 2 – y 1 x 2 – x 1 4 – 4 4 – (–2) = 0 6 = = 0 Write formula for slope. Substitute. Simplify.

3. EXAMPLE 4 Find the slope of a vertical line Find the slope of the line shown. Let (x 1, y 1 ) = (3, 5) and (x 2, y 2 ) = (3, 1). m = y 2 – y 1 x 2 – x 1 Write formula for slope. 1 – 5 3 – 3 = Substitute. Division by zero is undefined. ANSWER Because division by zero is undefined, the slope of a vertical line is undefined. – 4 0 =

4. EXAMPLE 2 Write an equation from a graph GUIDED PRACTICE for Examples 2, 3 and 4 Find the slope of the line that passes through the points. 4. (5, 2) and (5, –2) ANSWERundefined

5. Write an equation from a graph GUIDED PRACTICE for Examples 2, 3 and 4 5. (0, 4) and (–3, 4) Find the slope of the line that passes through the points. 0 ANSWER

6. Write an equation from a graph GUIDED PRACTICE for Examples 2, 3 and 4 6. (0, 6) and (5, –4) Find the slope of the line that passes through the points. ANSWER –2–2