Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 6 - Applications of the Integral - 6.1 Area Between Two Curves - Exercises - Page 286: 9

Answer

$$\frac{4}{3}$$

Work Step by Step

Since \begin{aligned} y_{1}(x) &=y_{2}(x) \\ x^{3}-x &=1-x^{2} \\ x^{3}+x^{2}-x-1 &=0 \\ (x-1)(x+1)^{2} &=0 \\ x=\pm 1 \end{aligned} Then \begin{aligned} A &=\int_{-1}^{1}\left(y_{1}-y_{2}\right) d x \\ &=\int_{-1}^{1}\left(\left(1-x^{2}\right)-x\left(x^{2}-1\right)\right) d x \\ &=\int_{-1}^{1}\left(\left(1-x^{2}\right)-x\left(x^{2}-1\right)\right) d x \\ &=\left(-x^{3}-x^{2}+x+1\right) d x \\ &=\left.\left(-\frac{x^{4}}{4}-\frac{x^{3}}{3}+\frac{x^{2}}{2}+x\right)\right|_{-1} ^{1} \\ &=\left(-\frac{1}{4}-\frac{1}{3}+\frac{1}{2}+1\right)-\left(-\frac{1}{4}-\frac{-1}{3}+\frac{1}{2}-1\right) \\ &=\frac{4}{3} \end{aligned}
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