College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 1, Equations and Graphs - Section 1.6 - Solving Other Types of Equations - 1.6 Exercises - Page 139: 72

Answer

The solutions are $x=-\sqrt{7}$ and $x=\sqrt{7}$

Work Step by Step

$\sqrt{11-x^2}-\dfrac{2}{\sqrt{11-x^2}}=1\hspace{0.7cm}{\color{blue}{\text{Given equation}}}$ $\Rightarrow \sqrt{11-x^2}\times (\sqrt{11-x^2}-\dfrac{2}{\sqrt{11-x^2}})=\sqrt{11-x^2}$ $\Rightarrow (\sqrt{11-x^2})^2-2=\sqrt{11-x^2}$ $\Rightarrow (\sqrt{11-x^2})^2-2-\sqrt{11-x^2}=0$ $\Rightarrow (\sqrt{11-x^2})^2-\sqrt{11-x^2}-2=0$ $\Rightarrow \bigg(\sqrt{11-x^2}-2\bigg)\bigg(\sqrt{11-x^2}+1\bigg)=0$ $\Rightarrow\sqrt{11-x^2}-2=0\Rightarrow \sqrt{11-x^2}=2\Rightarrow 11-x^2=4$ $\Rightarrow -x^2=4-11\Rightarrow-x^2=-7\Rightarrow x^2=7\Rightarrow x=\pm\sqrt{7}$ $\text{or }\sqrt{11-x^2}+1=0\Rightarrow \sqrt{11-x^2}=-1 \hspace{0.3cm}{\color{red}{reject}}$ The solutions are $x=-\sqrt{7}$ and $x=\sqrt{7}$
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