Pre-Algebra Demystified

CHAPTER 11 Graphing 223

SOLUTION

Let x 1 ¼5, y 1 ¼ 3, and x 2 ¼8, y 2 ¼1, and then substitute in the slope
formula:

m¼

y 2 
y 1

x 2 
x 1

¼

1
3

8
5

¼

2

3

¼

2

3

Hence, the slope of the line is
^23.
The slope whose equation is known can be found by selecting two points
on the line then using the slope formula.

EXAMPLE
Find the slope of a line whose equation is 5xþ2y¼10.

SOLUTION
Select two points on the line:

Let x¼4, then Let x¼
2, then

5xþ2y¼ 10 5xþ2y¼ 10

5(4)þ2y¼ 10 5 ð
 2 Þþ2y¼ 10

20 þ2y¼ 10 
 10 þ2y¼ 10

20 
 20 þ2y¼ 10 
 20 
 10 þ 10 þ2y¼ 10 þ 10

2y¼
 10 2y¼ 20

2 y

2

¼

10

2

2 y

2

¼

20

2

y¼
5y¼ 10

ð 4 ;
 5 Þð
 2 ; 10 Þ

Fig. 11-25.