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: 35

Answer

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

Work Step by Step

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