Calculus with Applications (10th Edition)

Published by Pearson
ISBN 10: 0321749006
ISBN 13: 978-0-32174-900-0

Chapter 4 - Calculating the Derivative - 4.3 The Chain Rule - 4.3 Exercises - Page 225: 32

Answer

$\displaystyle \frac{dy}{dx}=x(x^{2}-1)^{3}(11x^{3} -3x+16)$

Work Step by Step

Use the product rule $\color{blue}{[u(x)\cdot v(x)]^{\prime}=u(x)\cdot v^{\prime}(x)+v(x)\cdot u^{\prime}(x)}$ For $v^{\prime}(x)$, we need the chain rule. $\left[\begin{array}{llll} u(x)=x^{3}+2 & , & v(x)=(x^{2}-1)^{4} & \\ u^{\prime}(t)=3x^{2} & & v^{\prime}(x)=[w(x)]^{4} & \\ & & v^{\prime}(x)=4\cdot[w(x)]^{3}\cdot w^{\prime}(x) & (\text{chain rule)})\\ & & v^{\prime}(x)=4(x^{2}-1)^{3}\cdot 2x & \end{array}\right]$ $\displaystyle \frac{dy}{dx}=u(x)\cdot v^{\prime}(x)+v(x)\cdot u^{\prime}(x)$ $=(x^{3}+2)[4(x^{2}-1)^{3}\cdot 2x]+(x^{2}-1)^{4}(3x^{2})$ $=8x(x^{3}+2)(x^{2}-1)^{3}+3x^{2}(x^{2}-1)^{4}$ $=x(x^{2}-1)^{3}[8(x^{3}+2)+3x(x^{2}-1)]$ $=x(x^{2}-1)^{3}(8x^{3}+16+3x^{3}-3x)$ $=x(x^{2}-1)^{3}(11x^{3} -3x+16)$
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