1. Geometry Section 3.6 “Slope of Parallel and Perpendicular lines”

2. Recall how to find the slope of a line through two points (x 1, y 1 ) and (x 2, y 2 ). m =

3. When working with the graph of a line, you may prefer to think of slope as ____________

4. Example: Find the slope of the line through each pair of points. 1. (-2, -3) (5, 7) 2. (-3, 2) (4, -6) 3. (5, -4) (5, 6) 4. (8, -1) (13, -1)

5. If the slope of a line is positive, then __________________________ If the slope of a line is negative, then __________________________ If the slope of a line is zero, then ____________________ If the slope of a line is undefined, then ____________________

6. Example: Find y so that the slope of the line through the points (5, y) and (-3, 4) is

7. Two nonvertical lines are parallel if __________________ Note: Vertical lines are parallel, but since their slopes are undefined, we can’t say the slopes are equal.

8. Two lines, neither of which is vertical, are perpendicular if ________________________________

9. Example: Give the slope of a line parallel to a line with the given slope and give the slope of a line perpendicular to a line with the given slope.