Precalculus (6th Edition) Blitzer

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

Chapter 7 - Section 7.4 - Systems of Nonlinear Equations in Two Variables - Exercise Set - Page 851: 52

Answer

The solution is $\left\{ \left( -1,-\frac{1}{3} \right),\left( -1,\frac{1}{3} \right),\left( 1,\frac{-1}{3} \right),\left( 1,\frac{1}{3} \right) \right\}$

Work Step by Step

The provided equations are, $\begin{align} & \frac{2}{{{x}^{2}}}+\frac{1}{{{y}^{2}}}=11\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \left( \text{I} \right) \\ & \frac{4}{{{x}^{2}}}-\frac{2}{{{y}^{2}}}=-14\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \left( \text{II} \right) \end{align}$ Multiply the equation (I) by (II) and add the equation (I) and equation (II): $\begin{align} & \frac{4}{{{x}^{2}}}+\frac{2}{{{y}^{2}}}=22 \\ & \frac{4}{{{x}^{2}}}-\frac{2}{{{y}^{2}}}=-14 \\ & \overline{\begin{align} & \,\,\,\,\,\,\frac{8}{{{x}^{2}}}=8\,\,\,\,\,\,\,\,\,\,\,\,\, \\ & x=\pm 1 \end{align}} \\ \end{align}$ Substitute the value of $ x=1,x=-1$ in equation (I) For $\begin{align} & x=-1; \\ & \frac{2}{{{\left( -1 \right)}^{2}}}+\frac{1}{{{y}^{2}}}=11 \\ & 2+\frac{1}{{{y}^{2}}}=11 \\ & {{y}^{2}}=\frac{1}{9} \end{align}$ Then, $ y=\pm \frac{1}{3}$ For $\begin{align} & x=1; \\ & \frac{2}{{{\left( 1 \right)}^{2}}}+\frac{1}{{{y}^{2}}}=11 \\ & 2+\frac{1}{{{y}^{2}}}=11 \\ & {{y}^{2}}=\frac{1}{9} \end{align}$ Then, $ y=\pm \frac{1}{3}$ Thus, the solution set of system is $\left\{ \left( -1,-\frac{1}{3} \right),\left( -1,\frac{1}{3} \right),\left( 1,\frac{-1}{3} \right),\left( 1,\frac{1}{3} \right) \right\}$.
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