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: 81

Answer

$$x=\dfrac{-2y\pm\sqrt{10y^2+4}}{2}$$ $$y=\dfrac{2x\pm\sqrt{10x^2-6}}{3}$$

Work Step by Step

To solve for $x$ in terms of $y$, first rewrite in standard quadratic equation form: $ax^2 + bx +c=0$ $2x^2+4xy-3y^2-2=0$ where $a=2$, $b=4y$, and $c=(-3y^2-2)$ now, apply the quadratic formula: $x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ $x=\dfrac{(-)(4y)\pm\sqrt{(4y)^2-4(2)(-3y^2-2)}}{2(2)}$ $x=\dfrac{-4y\pm\sqrt{16y^2-8(-3y^2-2)}}{4}$ $x=\dfrac{-4y\pm\sqrt{16y^2+24y^2+16}}{4}$ $x=\dfrac{-4y\pm\sqrt{40y^2+16}}{4}$ $x=\dfrac{-4y\pm\sqrt{(4)(10y^2+4)}}{4}$ $x=\dfrac{-4y\pm2\sqrt{10y^2+4}}{4}$ $$x=\dfrac{-2y\pm\sqrt{10y^2+4}}{2}$$ To solve for $y$ in terms of $x$, first rewrite in standard quadratic equation form: $ay^2 + by +c=0$ $-3y^2+4xy+2x^2-2=0$ where $a=-3$, $b=4x$, and $c=(2x^2-2)$ now, apply the quadratic formula: $y=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ $y=\dfrac{(-)(4x)\pm\sqrt{(4x)^2-4(-3)(2x^2-2)}}{2(-3)}$ $y=\dfrac{-4x\pm\sqrt{16x^2+12(2x^2-2)}}{-6}$ $y=\dfrac{-4x\pm\sqrt{16x^2+24x^2-24}}{-6}$ $y=\dfrac{-4x\pm\sqrt{40x^2-24}}{-6}$ $y=\dfrac{-4x\pm\sqrt{(4)(10x^2-6)}}{-6}$ $y=\dfrac{-4x\pm2\sqrt{10x^2-6}}{-6}$ $y=\dfrac{-2x\pm\sqrt{10x^2-6}}{-3}$ $$y=\dfrac{2x\pm\sqrt{10x^2-6}}{3}$$
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