Finite Math and Applied Calculus (6th Edition)

Published by Brooks Cole
ISBN 10: 1133607705
ISBN 13: 978-1-13360-770-0

Chapter 11 - Section 11.4 - The Chain Rule - Exercises - Page 831: 29

Answer

$h^{\prime}(x)=-[(x+1)(x^{2}-1)]^{-3/2}\cdot(x+1)(3x-1)$

Work Step by Step

h(x) is a composite function multiplied with a constant, 2. $u(v(x))=[(x+1)(x^{2}-1)]^{-1/2}$ The last calculation in this composition would be a power to (-1/2), so $u(x)=x^{-1/2},\displaystyle \qquad \frac{du}{dx}=-\frac{1}{2}x^{-3/2}$ $v(x)=(x+1)(x^{2}-1)$ , which is a product, ... $(fg)^{\prime}=f^{\prime}g+fg^{\prime}$ $\displaystyle \frac{dv}{dx}=(1)(x^{2}-1)+(x+1)(2x)$ $=x^{2}-1+2x^{2}+2x$ $=3x^{2}+2x-1$ Now, $h(x)=2u(v(x)), $ $h^{\prime}(x)=2\displaystyle \frac{du}{dv}\frac{dv}{dx}=$ $=2(-\displaystyle \frac{1}{2}v^{-3/2})\cdot(3x^{2}+2x-1)$ $=-[(x+1)(x^{2}-1)]^{-3/2}\cdot(3x^{2}+2x-1)$ Attempt to factor the last trinomial: search for 2 factors of $3(-1)=3$, with sum of 2...( 3 and $-1)$ $ 3x^{2}+2x-1=3x^{2}+3x-x-1$ $=3x(x+1)-(x+1)=(x+1)(3x-1)$ $h^{\prime}(x)=-[(x+1)(x^{2}-1)]^{-3/2}\cdot(x+1)(3x-1)$
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