Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 2 - Section 2.3 - Polynomial Functions and Their Graphs - Exercise Set - Page 349: 34

Answer

\[f\left( x \right)={{x}^{3}}-4x+2\] has a zero between 0 and 1.

Work Step by Step

Find $f\left( 0 \right)$ and $f\left( 1 \right)$. If the sign changes in the values of $f\left( 0 \right)$ and $f\left( 1 \right)$, then there must be at least one zero between 1 and 2. That is., $\begin{align} & f\left( x \right)={{x}^{3}}-4x+2 \\ & f\left( 0 \right)=0-4\times 0+2 \\ & f\left( 0 \right)=2, \\ \end{align}$ Which is a positive. And $\begin{align} & f\left( x \right)={{x}^{3}}-4x+2 \\ & f\left( 1 \right)=1-4+2 \\ & f\left( 1 \right)=-1, \\ \end{align}$ Which is a negative. Thus, there is a sign change in the value of $f\left( 0 \right)$ and $f\left( 1 \right)$ , and there is at least one zero between 0 and 1.
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