Pre-Algebra Demystified

5xþ2y¼ 30

5xþ 2 ð 0 Þ¼ 30

5xþ 0 ¼ 30

5x¼ 30

5x

5

¼

30

5

x¼ 6

Hence, the x intercept is (6, 0).

Math Note: It is easy to draw lines on a graph using the intercepts

for the two points.

PRACTICE

1. Find the x intercept of 5xþ4y¼ 30


2. Find the y intercept of x
   7y¼ 14


3. Find the y intercept of 2xþ8y¼ 24


4. Find the x intercept of 3x
   17y¼ 21


5. Find the y intercept of xþ5y¼
   20

ANSWERS

1. (6, 0)


2. (0,
   2)


3. (0, 3)


4. (7, 0)


5. (0,
   4)

Slope

An important concept associated with lines is called theslopeof a line. The
slope of a line is associated with the ‘‘steepness’’ of a line. Theslopeof a line
is the ratio of the vertical change to the horizontal change of a line when
going from left to right. The slope is loosely defined as the rise divided by the
run (see Fig. 11-23).
The slope of a line can be found in several ways. A line going uphill from
left to right has a slope that is positive. A line going downhill from left to
right has a slope that is negative. The slope of a horizontal line is zero and the
slope of a vertical line isundefined(see Fig. 11-24).

CHAPTER 11 Graphing 221