Calculus: Early Transcendentals 9th Edition

Published by Cengage Learning
ISBN 10: 1337613924
ISBN 13: 978-1-33761-392-7

Chapter 3 - Section 3.4 - The Chain Rule - 3.4 Exercises - Page 206: 6

Answer

$\frac{dy}{dx}=\frac{e^x}{3\sqrt[3]{(e^x+1)^2}}$

Work Step by Step

Considering $u=e^x+1$, the function can be written as $y=\sqrt[3]{u}$ or $y=u^{1/3}$. We have the composite function $y=f(g(x))$ where $g(x)=e^x+1$ and $f(u)=u^{1/3}$. Then, $\frac{dy}{dx}=\frac{dy}{du}\cdot \frac{du}{dx}$ (By the chain rule) $=\frac{d}{du}(u^{1/3})\cdot \frac{d}{dx}(e^x+1)$ $=\frac{1}{3}u^{-2/3}\cdot (e^x+0)$ $=\frac{1}{3\sqrt[3]{u^2}}\cdot e^x$ $=\frac{1}{3\sqrt[3]{(e^x+1)^2}}\cdot e^x$ $=\frac{e^x}{3\sqrt[3]{(e^x+1)^2}}$ Thus, $\frac{dy}{dx}=\frac{e^x}{3\sqrt[3]{(e^x+1)^2}}$
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