Pre-Algebra Demystified

On the graph of a line the slope can be found by selecting two points,

forming a right triangle, and then counting the number of units in the rise

and run and dividing those two values (see Fig. 11-25).

A better method is to find the coordinates of two points on the line, say

(x 1 ,y 1 ) and (x 2 ,y 2 ) and then use the formula:

slopeðmÞ¼

y 2 
y 1

x 2 
x 1

EXAMPLE

Find the slope of a line passing through the points whose coordinates are

(5, 3) and (8, 1).

222 CHAPTER 11 Graphing

Fig. 11-23.

Fig. 11-24.