Precalculus (6th Edition) Blitzer

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

Chapter 2 - Section 2.2 - Quadratic Functions - Exercise Set - Page 334: 110

Answer

The values are \[f\left( 2 \right)=-1\] and \[f\left( 3 \right)=16\]

Work Step by Step

To find $f\left( 2 \right)$ in the given function, replace $x=2$ in the provided equation: $\begin{align} & f\left( 2 \right)={{2}^{3}}-2\left( 2 \right)-5 \\ & =8-9 \\ & =-1 \end{align}$ To find $f\left( 3 \right),$ replace $x=3$ in the given equation: $\begin{align} & f\left( 3 \right)={{3}^{3}}-2\left( 3 \right)-5 \\ & =27-11 \\ & =16 \end{align}$ Since, $f\left( 2 \right)$ is negative and $f\left( 3 \right)$ is positive and the function is continuous, thus to go from $f\left( 2 \right)$ to $f\left( 3 \right)$ , the curve must cross the x-axis. Hence, the values are $f\left( 2 \right)=-1$ and $f\left( 3 \right)=16$.
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