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: 79

Answer

$$x=\dfrac{y\pm \sqrt{8-11y^2}}{4}$$ $$y=\dfrac{x\pm \sqrt{6-11x^2}}{3}$$

Work Step by Step

To solve for $x$ in terms of $y$, first rewrite in standard quadratic equation form: $ax^2 + bx+c=0$ $4x^2-2xy+3y^2-2$ where $a=4$, $b=-2y$, and $c=(3y^2-2)$ now, apply the quadratic formula $x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$ $x=\dfrac{(-)(-2y)\pm \sqrt{(-2y)^2-4(4)(3y^2-2)}}{2(4)}$ $x=\dfrac{2y\pm \sqrt{4y^2-16(3y^2-2)}}{8}$ $x=\dfrac{2y\pm \sqrt{4y^2-48y^2+32)}}{8}$ $x=\dfrac{2y\pm \sqrt{32-44y^2)}}{8}$ $x=\dfrac{2y\pm \sqrt{(4)(8-11y^2)}}{8}$ $x=\dfrac{2y\pm 2\sqrt{8-11y^2}}{8}$ $$x=\dfrac{y\pm \sqrt{8-11y^2}}{4}$$ To solve for $y$ in terms of $x$, first rewrite in standard quadratic equation form: $ay^2 + by+c=0$ $3y^2-2xy+4x^2-2=0$ where $a=3$, $b=-2x$, and $c=(4x^2-2)$ now, apply the quadratic formula $y=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$ $y=\dfrac{(-)(-2x)\pm \sqrt{(-2x)^2-4(3)(4x^2-2)}}{2(3)}$ $y=\dfrac{2x\pm \sqrt{4x^2-12(4x^2-2)}}{6}$ $y=\dfrac{2x\pm \sqrt{4x^2-48x^2+24)}}{6}$ $y=\dfrac{2x\pm \sqrt{24-44x^2)}}{6}$ $y=\dfrac{2x\pm \sqrt{4(6-11x^2)}}{6}$ $y=\dfrac{2x\pm 2\sqrt{6-11x^2}}{6}$ $$y=\dfrac{x\pm \sqrt{6-11x^2}}{3}$$
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