Precalculus (6th Edition) Blitzer

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

Chapter P - Test: 18

Answer

The simplified form of the expression $\frac{2x\sqrt{{{x}^{2}}+5}-\frac{2{{x}^{3}}}{\sqrt{{{x}^{2}}+5}}}{{{x}^{2}}+5}$ is $\frac{10x}{\sqrt{{{\left( {{x}^{2}}+5 \right)}^{3}}}}$.

Work Step by Step

Consider the expression: $\frac{2x\sqrt{{{x}^{2}}+5}-\frac{2{{x}^{3}}}{\sqrt{{{x}^{2}}+5}}}{{{x}^{2}}+5}$ Multiply the numerator as well as the denominator by $\sqrt{{{x}^{2}}+5}$ $\begin{align} & \frac{2x\sqrt{{{x}^{2}}+5}-\frac{2{{x}^{3}}}{\sqrt{{{x}^{2}}+5}}}{{{x}^{2}}+5}=\frac{\left( 2x\sqrt{{{x}^{2}}+5}-\frac{2{{x}^{3}}}{\sqrt{{{x}^{2}}+5}} \right)\sqrt{{{x}^{2}}+5}}{{{x}^{2}}+5\cdot \sqrt{{{x}^{2}}+5}} \\ & =\frac{\left( 2x\sqrt{{{x}^{2}}+5}\cdot \sqrt{{{x}^{2}}+5}-\frac{2{{x}^{3}}}{\sqrt{{{x}^{2}}+5}}\cdot \sqrt{{{x}^{2}}+5} \right)}{{{x}^{2}}+5\cdot \sqrt{{{x}^{2}}+5}} \\ & =\frac{2x\left( {{x}^{2}}+5 \right)-2{{x}^{3}}}{\sqrt{{{\left( {{x}^{2}}+5 \right)}^{3}}}} \end{align}$ On further simplification: $\begin{align} & \frac{2x\sqrt{{{x}^{2}}+5}-\frac{2{{x}^{3}}}{\sqrt{{{x}^{2}}+5}}}{{{x}^{2}}+5}=\frac{2{{x}^{3}}+10x-2{{x}^{3}}}{\sqrt{{{\left( {{x}^{2}}+5 \right)}^{3}}}} \\ & =\frac{10x}{\sqrt{{{\left( {{x}^{2}}+5 \right)}^{3}}}} \end{align}$ Therefore, the simplified form of the expression $\frac{2x\sqrt{{{x}^{2}}+5}-\frac{2{{x}^{3}}}{\sqrt{{{x}^{2}}+5}}}{{{x}^{2}}+5}$ is $\frac{10x}{\sqrt{{{\left( {{x}^{2}}+5 \right)}^{3}}}}$.
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