1. 3-3 Slopes of Lines
Slope is the ratio of the rise (the vertical change) over the run (the horizontal change).
Sometimes they will give you a graph, pick points that are integers.
Sometimes they will just give you the numbers.

2. Find the slope of each line
(0,2) and (2,0)
(5,2) and (-6,-1)

3. Try These
1. (-3,4) and (2,5)
2. (0,-4) and (1,2)
1. 1/5
2. 6

4. What the slope looks like
Positive Slope m>0
Negative Slope m<0
Undefined Slope
m is undefined (can’t divide by 0)
0 Slope
m = 0

5. Parallel and Perpendicular Lines
Postulate 3.2: Two distinct nonvertical lines have the same slope if and only if they are parallel.
All vertical lines are parallel.
Postulate 3.3: Two nonvertical lines are perpendicular if and only if the product of their slopes is –1.
Perpendicular lines have opposite reciprocal slopes.
Ex: m = 6, m = -1/6

6. Example
Given the points A(-2, -1/2), B(2, ½), C(5,0) and D(4,4) describe how AB is related to CD.
¼ and –4 are not the same so they are not parallel.
¼(-4) =-1 so the lines are perpendicular.

7. Try These
Page 160, #1-8, check them with me, then proceed to your homework assignment.
#20 p even, 40-42, 48-50