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: 148


Hence, by using the formula college students spend in $2011$ is $\$ 89.6$. which is overestimates by $ \$ 2.6 $ billion.

Work Step by Step

From the question we have $D(x)=1.2x^2+1.6(x+40)$, Where, $D$ is discretionary spending in billions of dollars and $x$ is years after $2007$. Therefore, the value of $x$ for the year $ 2011 $ is $ =2011-2007 =4 $. plug in $x=4$ into the formula. $D(4)=1.2(4)^2+1.6(4+40)$. Clear the parentheses. $ D(4)=1.2\times 16+6.4+64 $. Simplify. $ D(4)=89.6 $. By observing the graph the value of $D(4)$ is $87$ billions of dollars. Hence, the model overestimates the actual value by $87-89.6=-2.6$ billions of dollars.
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