Precalculus (6th Edition) Blitzer

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

Chapter 1 - Section 1.2 - Basics of Functions and Their Graphs - Exercise Set - Page 176: 36

Answer

a) $\frac{33}{8}$ b) $\frac{31}{8}$ c) $\frac{-4{{x}^{3}}+1}{-{{x}^{3}}}$

Work Step by Step

(a) Let us consider the function $f\left( x \right)=\frac{4{{x}^{3}}+1}{{{x}^{3}}}$. By putting the value of $x$ as $2$ in the equation of $f\left( x \right)$ we obtain the value of $f\left( 2 \right)$ as: $\begin{align} & f\left( x \right)=\frac{4{{x}^{3}}+1}{{{x}^{3}}} \\ & f\left( 2 \right)=\frac{4\cdot {{2}^{3}}+1}{{{2}^{3}}} \\ & =\frac{4\cdot 8+1}{8} \\ & =\frac{33}{8} \end{align}$ Hence, the value of $f\left( 2 \right)$ is $\frac{33}{8}$. (b) Let us consider the function $f\left( x \right)=\frac{4{{x}^{3}}+1}{{{x}^{3}}}$. By putting the value of $x$ as $-2$ in the equation of $f\left( x \right)$ we obtain the value of $f\left( -2 \right)$ as: $\begin{align} & f\left( x \right)=\frac{4{{x}^{3}}+1}{{{x}^{3}}} \\ & f\left( -2 \right)=\frac{4\cdot {{\left( -2 \right)}^{3}}+1}{{{\left( -2 \right)}^{3}}} \\ & =\frac{-4\cdot 8+1}{-8} \\ & =\frac{-31}{-8} \end{align}$ $=\frac{31}{8}$ Hence, the value of $f\left( -2 \right)$ is $\frac{31}{8}$. (c) Let us consider the function $f\left( x \right)=\frac{4{{x}^{3}}+1}{{{x}^{3}}}$. By putting the value of $x$ as $-x$ in the equation of $f\left( x \right)$ we obtain the value of $f\left( -x \right)$ as: $\begin{align} & f\left( x \right)=\frac{4{{x}^{3}}+1}{{{x}^{3}}} \\ & f\left( -x \right)=\frac{4\cdot {{\left( -x \right)}^{3}}+1}{{{\left( -x \right)}^{3}}} \\ & =\frac{-4{{x}^{3}}+1}{-{{x}^{3}}} \end{align}$ Hence, the value of $f\left( -x \right)$ is $\frac{-4{{x}^{3}}+1}{-{{x}^{3}}}$.
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