Beginning Algebra, 11th Edition

68. 2 x- 5 y= 10 69.y+ 4 = 0 70.x- 5 = 0

SECTION 3.1 Linear Equations in Two Variables; The Rectangular Coordinate System 185

xy

0

0

5

• 3


• 
  

xy

0

5

2

• 3


• 
  

xy

1

0

6

• 4

71.Look at your graphs of the ordered pairs in Exercises 65–70.Describe the pattern indi-

cated by the plotted points.

72. (a)A line through the plotted points in Exercise 69would be horizontal. What do you
    notice about the y-coordinates of the ordered pairs?
    (b)A line through the plotted points in Exercise 70would be vertical. What do you
    notice about the x-coordinates of the ordered pairs?

Solve each problem. See Example 6.

73.It costs a flat fee of $20 plus $5 per day to rent a pressure washer. Therefore, the cost to

rent the pressure washer for xdays is given by

where yis in dollars. Express each of the following as an ordered pair.

(a)When the washer is rented for 5 days, the cost is $45.

(b)I paid $50 when I returned the washer, so I must have rented it for 6 days.

74.Suppose that it costs $5000 to start up a business selling snow cones. Furthermore, it

costs $0.50 per cone in labor, ice, syrup, and overhead. Then the cost to make xsnow

cones is given by ydollars, where

Express each of the following as an ordered pair.

(a)When 100 snow cones are made, the cost is $5050.

(b)When the cost is $6000, the number of snow cones made is 2000.

75.The table shows the rate (in percent) at which

2-year college students (public) completed a

degree within 3 years.

y=0.50x+5000.

y= 5 x+20,

Year Percent

2002 31.6

2003 30.1

2004 29.0

2005 27.5

2006 26.6

2007 26.9

Source:ACT.

(a)Write the data from the table as ordered

pairs where xrepresents the year and

yrepresents the percent.

(b)What does the ordered pair mean in the context of this problem?

(c)Make a scatter diagram of the data, using the ordered pairs from part (a) and the given

grid.

(d)Describe the pattern indicated by the points on the scatter diagram. What is happening

to rates at which 2-year college students complete a degree within 3 years?

1 2007, 26.9 2

1 x, y 2 ,

y

x

30

31

32

29

28

27

26

(^020022004)
Year
2006
2-YEAR COLLEGE STUDENTS
COMPLETING A DEGREE
WITHIN 3 YEARS
Percent (%)