1. Lesson 3 – 3 Slopes of Lines
Geometry
Lesson 3 – 3
Slopes of Lines
Objective:
Find slope of lines.
Use slope to identify parallel and perpendicular lines.

2. Slope

3. Find the slope 4 5 -6 3

4. Find the slope
= 0
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5. Slope
Positive Slope
Negative Slope
Zero Slope
Undefined Slope

6. Rate of Change
Rate of change describes how a quantity y changes in relationship to quantity x.
Fancy word for slope in word problems.

7. A pilot flies a plane from Columbus, Ohio, to Orlando, Florida. After 0.5 hour, the plane reaches its cruising altitude and is 620 miles from Orlando. Half an hour later, the plane is 450 miles from Orlando. How far was the plane from Orlando 1.25 hours after take off.

8. (0.5, 620), (1, 450) Need to write an equation for the info.
A pilot flies a plane from Columbus, Ohio, to Orlando, Florida. After 0.5 hour, the plane reaches its cruising altitude and is 620 miles from Orlando. Half an hour later, the plane is 450 miles from Orlando. How far was the plane from Orlando 1.25 hours after take off.
Need to write an equation for the info.
Can you identify 2 points?
(0.5, 620), (1, 450)
Cannot have a decimal or fraction in a fraction.
= -340
= mph
Or 340 mph decrease
Cont…

9. 450 = -340(1) + b y = -340x + 790 Slope-Intercept form: y = mx + b
A pilot flies a plane from Columbus, Ohio, to Orlando, Florida. After 0.5 hour, the plane reaches its cruising altitude and is 620 miles from Orlando. Half an hour later, the plane is 450 miles from Orlando. How far was the plane from Orlando 1.25 hours after take off.
Slope-Intercept form: y = mx + b
Plug in either point and slope to find b.
450 = -340(1) + b
450 = b
790 = b
y = -340x + 790
How far was the plane from Orlando 1.25 hours after take off?
y = -340(1.25) + 790 =
= 365 miles

10. Slope: Parallel and Perpendicular Lines
Slopes of Parallel Lines
Two nonvertical lines have the same slope if and only if they are parallel. All vertical lines are parallel.
Slopes of Perpendicular Lines
Two nonvertical lines are perpendicular if and only if the product of their slopes are –1. Vertical and horizontal lines are perpendicular.
Slopes are opposite reciprocals.

11. Determine whether AB and CD are parallel, perpendicular, or neither.
A (14, 13) B (-11, 0) C (-3, 7) D (-4, -5)
Need to have both
Slopes and answer
Neither

12. Determine whether AB and CD are parallel, perpendicular, or neither.
A (3, 6) B (-9, 2) C (5, 4) D (2, 3)
Parallel

13. Determine whether AB and CD are parallel, perpendicular, or neither.
A (1,1) B (-1, -5) C (3, 2) D (6, 1)
Perpendicular

14. Graph the line that contains A (-3, 0) and is perpendicular to CD with C (-2, -3) and D (2, 0)
So a line AB perpendicular to line CD would have a
slope of what?

15. Homework
Pg – 11 all, 12 – 48 EOE