Calculus (3rd Edition)

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

Chapter 4 - Applications of the Derivative - 4.2 Extreme Values - Exercises - Page 181: 30

Answer

Minimum value is $ f(-2)=-2$ and maximum value is $ f(2)=10$

Work Step by Step

First, we find the critical points of $ y $. $ f'(x)=3x^{2}+2x-1$ is differentiable everywhere. However, $ f'(x)= 0$ when $ x=-1$ or $ x=\frac{1}{3}$. That is, $-1$ and $\frac{1}{3}$ are the critical points of $ y $. Now, we compare the values of $ f(x)$ at the critical points and the end points. $ f(-1)=(-1)^{3}+(-1)^{2}-(-1)=1$ $ f(\frac{1}{3})=(\frac{1}{3})^{3}+(\frac{1}{3})^{2}-\frac{1}{3}=-\frac{5}{27}$ $ f(-2)=(-2)^{3}+(-2)^{2}-(-2)=-2$ $ f(2)=2^{3}+2^{2}-2=10$ Minimum value is $ f(-2)=-2$ and maximum value is $ f(2)=10$
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