1. 2.2 Slope and Rate of Change
Algebra 2
Mrs. Spitz
Fall 2009

2. Objectives
Find slopes of lines and classify parallel and perpendicular lines.
Use slope to solve problems, such as how to safely adjust a ladder.

3. Assignment
pp #4-47 all

4. The slope of a nonvertical line is the ratio of vertical change (the rise) to the horizontal change (the run).
The slope of a line is represented by the letter m.
Just like any 2 points determine a line, any 2 points are all that are needed to determine the slope.
The slope of the line is the same regardless of which 2 points are used

5. The slope of a line
The slope of a nonvertical line passing thru the points (x1,y1) (x2,y2):

6. Find the slope of a line passing thru (-3,5) & (2,1)

7. Classification of lines by slope
A line with positive slope: rises from left to right (m>0)
A line with negative slope: falls from left to right (m<0)
A line with slope of zero is horizontal (m=0)
A line with undefined slope is vertical (m is undefined)

8. W/out graphing, tell whether the line thru the points rises, falls, horizontal, or vertical.
1) (3,-4), (1,-6)
2) (2,-1), (2,5)
m>0, the line rises
Undefined:
The line is
vertical

9. Not only does slope tell you whether the line rises, falls, is horizontal, or is vertical; it also tells you the steepness of the line
For two lines, the line slope of greater absolute value is steeper.

10. Tell which line is steeper
Line 1 thru (2,3) & (4,7)
or Line 2 thru (-1,2) & (4,5)
Since the lines have positive slope &
m1>m2 line 1 is steeper