Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 3 - Applications of Differentiation - 3.2 The Mean Value Theorem - 3.2 Exercises - Page 220: 4

Answer

Rolle's theorem does not apply because $f(x)$ is not differentiable over the interval $[-1,1]$

Work Step by Step

We first look at $f(x)$ $f(x)=\sqrt((2-x^{\frac{2}{3}})^{3})$ Before we differentiate, we can rewrite $f(x)$ to make it easier to differentiate by combining the square root and the cube exponent $f(x)=(2-x^{\frac{2}{3}})^{\frac{3}{2}}$ $f′(x)=\frac{3}{2}(2-x^{\frac{2}{3}})^{\frac{1}{2}}*(-\frac{2}{3}x^{-\frac{1}{3}})$ $f′(x)=\frac{3\sqrt (2-x^{\frac{2}{3}})}{2}*-\frac{2}{3\sqrt[3] x}$ $f′(x)=-\frac{\sqrt (2-x\frac{2}{3})}{\sqrt[3] x}$ At $x=0$, $f′(x)$ is undefined, which makes $f(x)$ not differentiable, and Rolle's Theorem does not apply/.
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