Beginning Algebra, 11th Edition

(c) The model used in parts (a) and (b) was developed using the data in the

table below. How do the results in parts (a) and (b) compare to the actual

data from the table?

SECTION 6.6 Applications of Quadratic Equations 405

Foreign-Born

Year Population (millions)

1930 14.2

1940 11.6

1950 10.3

1960 9.7

1970 9.6

1980 14.1

1990 19.8

2000 28.4

2007 37.3

From the table, the actual value for 1980 is 14.1 million. Our answer in part (a),

14.6 million, is slightly high. For 2007, the actual value is 37.3 million, so our an-

swer of 36.0 million in part (b) is somewhat low. NOW TRY

Complete solution available
on the Video Resources on DVD

6.6 EXERCISES

1.Concept Check To review the six problem-solving steps first introduced in Section 2.4,

complete each statement.

Step 1: the problem carefully.

Step 2: Assign a to represent the unknown value.

Step 3: Write a(n) using the variable expression(s).

Step 4: the equation.

Step 5: State the.

Step 6: the answer in the words of the problem.

2.A student solves an applied problem and gets 6 or for the length of the side of a

square. Which of these answers is reasonable? Explain.

In Exercises 3 – 6, a figure and a corresponding geometric formula are given. Using x as the

variable, complete Steps 3 – 6 for each problem. (Refer to the steps in Exercise 1as needed.)

- 3

3.

Area of a parallelogram:

The area of this parallelogram is 45 sq.

units. Find its base and height.

4.

Area of a triangle:

The area of this triangle is 60 sq. units.

Find its base and height.

a=

1

2

a=bh bh

x + 1

2 x + 1

x + 5

3 x + 6

NOW TRY
EXERCISE 5
Use the model in Example 5
to find the foreign-born pop-
ulation of the United States in
the year 2000. Give your an-
swer to the nearest tenth of a
million. How does it compare
to the actual value from the
table?

NOW TRY ANSWER

5. 29.0 million; The actual value is
   28.4 million, so the answer using
   the model is slightly high.