Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 5: Integrals - Section 5.6 - Definite Integral Substitutions and the Area Between Curves - Exercises 5.6 - Page 304: 62

Answer

$8$

Work Step by Step

Expressing the $x$'s as functions of $y$, $x=f(y)=3-y^{2},$ $x=g(y)=-y^{2}/4$ Graphing the functions, we find the intersection points at $x=-2$ and $x=2$. Over the interval $y\in[-2,2],\ f(y)$ is to the right of $g(y)$, so $A=\displaystyle \int_{-2}^{2}[f(y)-g(y)]dy=\int_{-2}^{2}[3-y^{2}-(-\frac{y^{2}}{4})]dy$ $=\displaystyle \int_{-2}^{2}[3-\frac{3}{4}y^{2}]dy$ $=\displaystyle \left[3y-\frac{3}{4}\cdot\frac{y^{3}}{3} \right]_{-2}^{2}$ $=3(2+2)-\displaystyle \frac{1}{4}\cdot(8+8)$ =$8$
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