Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 1 - Graphs - Chapter Review - Chapter Test - Page 42: 6

Answer

The $x-$intercepts are $3,\,-3$, and the $y-$intercept is $9$. The graph of the equation ${{x}^{2}}+y=9$ is symmetric about the $y-$axis.

Work Step by Step

To determine the $x$-intercepts, substitute $y=0$ in the equation ${{x}^{2}}+y=9$, and solve for $x$. By substituting $y=0$ in ${{x}^{2}}+y=9$, ${{x}^{2}}+0=9$. By simplifying, $\Rightarrow {{x}^{2}}=9$. By taking the square root, $\Rightarrow x=\pm \,3$. Therefore, the $x$- intercepts are $3$ and $-3$. To determine the $y$-intercepts, substitute $x=0$ in the equation ${{x}^{2}}+y=9$, and solve for $y$. By substituting $x=0$ in ${{x}^{2}}+y=9$, ${{\left( 0 \right)}^{2}}+y=9$. By simplifying, $\Rightarrow 0+y=9$. $\Rightarrow y=9$. Therefore, the $y$-intercept is $9$. Now, test for symmetry: For the $x-$axis: Replace $y$ with $-y$ in the equation ${{x}^{2}}+y=9$. It gives ${{x}^{2}}-y=9$, which is not equal to ${{x}^{2}}+y=9$. For the $y-$axis: Replace $x$ with $-x$ in the equation ${{x}^{2}}+y=9$. It gives ${{\left( -x \right)}^{2}}+y=9$, which is equivalent to ${{x}^{2}}+y=9$. So, the graph of the equation ${{x}^{2}}+y=9$ is symmetric with respect to the $y-$axis. For the origin: Replace $x$ with $-x$ and $y$ with $-y$ in the equation ${{x}^{2}}+y=9$. It gives ${{\left( -x \right)}^{2}}+\left( -y \right)=9$, which is not equal to ${{x}^{2}}+y=9$. Hence, the graph of the equation ${{x}^{2}}+y=9$ is symmetric with respect to the $y-$axis.
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