Line
#1 Slope = 2 |
Line
#2 Slope = 0.5 |
Line
#3 Slope = -1.5 |
Algebra I
Lesson 6-1: Slope
Slope is a number that describes the steepness (or slant) of a line. A horizontal (flat) line has a slope of zero. From there, the higher the number, the steeper the line. Here are some examples:
| Line
#1 Slope = 2 |
Line
#2 Slope = 0.5 |
Line
#3 Slope = -1.5 |
There are two common methods to calculate the slope of a line. Both methods use the fact that slope is the ratio (fraction) "rise over run".
Method 1: Count Gridlines
On a graph, put a dot on two points of the line that are easy to identify (where two grid lines meet). Then count gridlines to get the "rise" and the "run" like shown in the picture below.
Line #2
|
Method 2: Use the "M" Formula
Points can also be identified by their (x,y) coordinates. There is a formula in Algebra that uses these coordinates to calculate the slope. From the picture above of Line #2 the two points are: Point #1 (-2,-1) and Point #2 (2,1). The "M" formula is:
 We say "m equals y sub 2 minus y sub 1 over x sub 2 minus x sub 1". |
m stands for slope. Using our points, our equation would be:
| On Your Own Try both Method 1 and Method 2 to calculate the slope of Line #1 above. You should get a slope of 2 for both calculations. |
Keys to remember:
