College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 5 - Systems of Equations and Inequalities - Exercise Set 5.4 - Page 559: 23

Answer

$\{\ (2,1),\ (2, -1),\ (-2,1),\ (-2, -1)\ \}$

Work Step by Step

1. Eliminating: Rewrite the equations so the constants are on the RHS. Eliminate the $(y^{2})$ terms: $\left\{\begin{array}{lll} 3x^{2}+4y^{2}=16 & , & /\times 3\\ 2x^{2}-3y^{2}=5 & , & /\times 4, add \end{array}\right.$ $(9+8)x^{2}=48+20$ $17x^{2}=68$ 2. Solving: $17x^{2}=68\qquad/\div 17$ $x^{2}=4$ $x=\pm 2$ 3. Back-substituting into $3x^{2}+4y^{2}=16$: $\left[\begin{array}{lll} x=2 & or & x=-2\\ 3(4)+4y^{2}=16 & & 3(4)+4y^{2}=16 \\ 4y^{2}=4 & & 4y^{2}=4\\ y^{2}=1 & & y^{2}=1\\ y=\pm 1 & & y=\pm 1 \end{array}\right]$ The solution set is $\{\ (2,1),\ (2, -1),\ (-2,1),\ (-2, -1)\ \}$
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