1. 3.4 Slopes of Lines September 27, 2011
BELLWORK #3­4
1. Find the value of x that make p // q. a
#1
(2x + 43) (3x)
p
x = 43 b
q
3. Can you prove a // b? yes
2. Which lines are parallel?
E F 4. If so, what theorem would you use?
95 80
Alt. Interior < Converse
85 100 5. Are you ready for the 3.1­3.3 Quiz
D G
on Wednesday? I hope so!
EF // DG
HW pg. 175 #3­9 odd, 13­29 odd 1

2. 3.4 Slopes of Lines September 27, 2011
3.4 Find and Use Slopes of Lines
Slope: ratio of vertical change (rise) to horizontal change (run)
between any 2 points.
run (x2 - x1)
Slope = rise change in y y -y
run
= change in x = x22 - x11 rise (y2 - y1)
Negative Slope: falls from left to right
Positive Slope: rises from left to right
Zero Slope: horizontal line
Undefined Slope: vertical line
HW pg. 175 #3­9 odd, 13­29 odd 2

3. 3.4 Slopes of Lines September 27, 2011
Comparing Slopes: When 2 lines intersect, the steeper line has
the slope with greater absolute value.
Postulate 17: Slopes of Parallel Lines
2 lines are // iff they have the same slope.
m1 = m2
Postulate 18: Slopes of Perpendicular Lines
2 lines are iff the product of their slopes is -1.
m1 * m2 = -1
HW pg. 175 #3­9 odd, 13­29 odd 3

4. 3.4 Slopes of Lines September 27, 2011
With your horizontal partner, complete #3 in guided practice.
HW pg. 175 #3­9 odd, 13­29 odd 4

5. 3.4 Slopes of Lines September 27, 2011
HW pg. 175 #3­9 odd, 13­29 odd 5

6. 3.4 Slopes of Lines September 27, 2011
HW pg. 175 #3­9 odd, 13­29 odd 6

7. 3.4 Slopes of Lines September 27, 2011
With your horizontal partner,
complete problems 4 & 5 in guided practice.
HW pg. 175 #3­9 odd, 13­29 odd 7

8. 3.4 Slopes of Lines September 27, 2011
HW pg. 175 #3-9 odd, 13-29 odd
HW pg. 175 #3­9 odd, 13­29 odd 8