Precalculus (10th Edition)

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

Chapter 1 - Graphs - 1.2 Graphs of Equations in Two Variables; Intercepts; Symmetry - 1.2 Assess Your Understanding - Page 18: 57

Answer

1) The $x$-intercept is $(-4,0)$, and the $y$-intercepts are $(0,2)$ and $(0,-2)$ 2) The graph of the equation ${{y}^{2}}=x+4$ is symmetric with respect to the $x$-axis. 3) The graph of the equation ${{y}^{2}}=x+4$ is not symmetric with respect to the $y$-axis, the $x$-axis, or the origin.

Work Step by Step

To find $x$-intercept(s), let $y=0$ $\Rightarrow \,0=x+4$ $\Rightarrow \,\,x=-4$. Therefore, the $x$-intercept is $(-4,0)$ To find the $y$-intercept(s), let $x=0$ $\Rightarrow \,\,{{y}^{2}}=0+4$ $\Rightarrow \,{{y}^{2}}=4$ $\Rightarrow \,\,y=\pm \,2$. The $y$-intercepts are $(0,2)$ and $(0,-2)$ To test for symmetry with respect to the $x$-axis, replace $y$ with $-y$. If it results in an expression equivalent to the original equation, then the equation is symmetric with respect to the $x$-axis. $\Rightarrow $${{(-y)}^{2}}=x+4$ is equivalent to ${{y}^{2}}=x+4$ Hence, the graph of the equation ${{y}^{2}}=x+4$ is symmetric with respect to the $x$-axis. To test for symmetry with respect to the $y$-axis, replace $x$ with –$x$. If it results in an expression equivalent to the original equation, then the equation is symmetric with respect to the $y$-axis. $\Rightarrow \,{{y}^{2}}=-x+4$ is not equivalent to ${{y}^{2}}=x+4$ Hence, the graph of the equation ${{y}^{2}}=x+4$ is not symmetric with respect to the $y$-axis. To test for symmetry with respect to the origin, replace $x$ with –$x$ and $y$ with $-y$. If it results in an expression equivalent to the original equation, then the equation is symmetric with respect to the origin. $\Rightarrow \,\,{{(-y)}^{2}}=-x+4$ $\Rightarrow \,{{y}^{2}}=-x+4$ is not equivalent to ${{y}^{2}}=x+4$. Hence, the graph of the equation ${{y}^{2}}=x+4$ is not symmetric with respect to the origin.
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