Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 1 - Section 1.2 - Operations with Real Numbers and Simplifying Algebraic Expressions - Exercise Set - Page 29: 147

Answer

Hence, the college students spend in 2013 is $ \$ 116.8 $ billion. The model underestimates by $ \$0.2 $ billion.

Work Step by Step

The given formula is $D(x)=1.2x^2+1.6(x+40)$, Where, $D$ is discretionary spending in billions of dollars and $x$ is years after $2007$. Therefore, the value of $x$ for the year $ 2013 $ is $ =2013-2017 =6 $. plug in $x=6$ into the formula. $D(6)=1.2(6)^2+1.6(6+40)$. Clear the parentheses. $ D(6)=1.2\times 36+9.6+64 $. Simplify. $ D(6)=116.8 $. By observing the graph the value of $D(6)$ is $117$ billions of dollars. Hence, the model underestimates the actual value by $117-116.8=0.2$ billions of dollars.
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