Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 1 - Equations and Inequalities - 1.4 Quadratic Equations - 1.4 Exercises - Page 122: 80

Answer

$x=\frac{2y\pm\sqrt {31y^2+9}}{9}$ $y=\frac{-2x\pm\sqrt {13x^2-1}}{3}$

Work Step by Step

Step 1. Rearrange the equation as a quadratic with $x$ as the variable: $9x^2-(4y)x-(3y^2+1)=0$ Step 2. Let $a=9, b=-4y, c=-(3y^2+1)$ and use the quadratic formula, we have: $x=\frac{4y\pm\sqrt {16y^2+4(9)(3y^2+1)}}{2(9)}=\frac{2y\pm\sqrt {31y^2+9}}{9}$ Step 3. Rearrange the equation as a quadratic with $y$ as the variable: $3y^2+(4x)y-(9x^2-1)=0$ Step 4. Let $a=3, b=4x, c=-(9x^2-1)$ and use the quadratic formula, we have: $y=\frac{-4x\pm\sqrt {16x^2+4(9x^2-1)}}{2(3)}=\frac{-2x\pm\sqrt {13x^2-1}}{3}$
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