Precalculus (6th Edition) Blitzer

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

Chapter 2 - Section 2.6 - Rational Functions and Their Graphs - Exercise Set - Page 399: 31

Answer

The vertical asymptote will be $x=-3$; there will be a hole at $x=3$.

Work Step by Step

Write $g\left( x \right)$ in the form of $\frac{p\left( x \right)}{q\left( x \right)}$. $\begin{align} & g\left( x \right)=\frac{x-3}{{{x}^{2}}-9} \\ & =\frac{p\left( x \right)}{q\left( x \right)} \end{align}$ So, $p\left( x \right)=x-3$ and $q\left( x \right)={{x}^{2}}-9$. For, the vertical asymptotes, put $q\left( x \right)=0$: $\begin{align} & q\left( x \right)={{x}^{2}}-9=0 \\ & {{x}^{2}}-9=0 \\ & \left( x-3 \right)\left( x+3 \right)=0 \end{align}$ Thus, the vertical asymptotes are $x=3,\text{ or }x=-3$ But, after rearranging, $x-3$ from the denominator will be eliminated. So, the vertical asymptote will be $x=-3$. To find the holes, observe the expression: $\begin{align} & g\left( x \right)=\frac{x-3}{{{x}^{2}}-9} \\ & =\frac{x-3}{\left( x-3 \right)\left( x+3 \right)} \\ & =\frac{1}{x+3} \end{align}$ Here, $x-3$ will be eliminated; when x approaches 3, the polynomial approaches to $\frac{1}{6}$ , but at the point $x=3$ the polynomial will be discontinuous. So, there will be a hole at $x=3$. Therefore, the vertical asymptote will be $x=-3$; there will be a hole at $x=3$. Hence, the vertical asymptote will be $x=-3$; there will be a hole at $x=3$.
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