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: 34

Answer

The vertical asymptote will be $x=4$; there will be a hole at $x=-6$.

Work Step by Step

Write $h\left( x \right)$ in the form of $\frac{p\left( x \right)}{q\left( x \right)}$. $\begin{align} & h\left( x \right)=\frac{x+6}{{{x}^{2}}+2x-24} \\ & =\frac{p\left( x \right)}{q\left( x \right)} \end{align}$ So, $p\left( x \right)=x+6$ and $q\left( x \right)={{x}^{2}}+2x-24$. For the vertical asymptotes, put $q\left( x \right)=0$: $\begin{align} & q\left( x \right)={{x}^{2}}+2x-24=0 \\ & {{x}^{2}}+2x-24=0 \\ & \left( x+6 \right)\left( x-4 \right)=0 \end{align}$ Therefore, the vertical asymptotes are $x=-6,\text{ or }x=4$. But, after rearranging, $x+6$ from the denominator will be eliminated. So, the vertical asymptote will be $x=-4$. To find the holes, observe the expression: $\begin{align} & h\left( x \right)=\frac{x+6}{{{x}^{2}}+2x-24} \\ & =\frac{x+6}{\left( x+6 \right)\left( x-4 \right)} \\ & =\frac{1}{x-4} \end{align}$ Here, $x+6$ will be eliminated; when x approaches $-6$ , the polynomial approaches to $-\frac{1}{10}$ but at the point $x=-6$ the polynomial will be discontinuous. So, there will be a hole at $x=-6$ Thus, the vertical asymptote will be $x=4$; there will be a hole at $x=-6$.
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