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: 59

Answer

$\displaystyle \frac{104}{15}$

Work Step by Step

Expressing the $y$'s as functions of $x$, $y=f(x)=4-4x^{2},$ $y=g(x)=x^{4}-1.$ Graphing the functions, we find the intersection points at $x=-1$ and $x=1$. Over the interval $x\in[-1,1],\ f(x)$ is above $g(x)$, so $A=\displaystyle \int_{a}^{b}(y_{above}-y_{below})dx=\int_{-1}^{1}[4-4x^{2}-(x^{4}-1)]dx$. $=\displaystyle \int_{-1}^{1}[5-4x^{2}-x^{4}]dx$. $=\displaystyle \left[5x-\frac{4x^{3}}{3}-\frac{x^{5}}{5} \right]_{-1}^{1}$ $=5(1+1)-\displaystyle \frac{4}{3}(1+1)-\frac{1}{5}(1+1)$ $=10-\displaystyle \frac{8}{3}-\frac{2}{5}$ $=\displaystyle \frac{104}{15}$
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