Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 8 - Summary Exercises - Applying Methods for Solving Quadratic Equations - Page 531: 20

Answer

$\left\{\dfrac{1-\sqrt{5}}{4},\dfrac{1+\sqrt{5}}{4}\right\}$

Work Step by Step

In the form $ax^2+bx+c=0,$ the given equation, $ 8x^2-4x=2 ,$ is equivalent to \begin{align*} 8x^2-4x-2&=0 \\\\ \dfrac{8x^2-4x-2}{2}&=\dfrac{0}{2} \\\\ 4x^2-2x-1&=0 .\end{align*} The equation above has \begin{align*} a= 4 ,\text{ }b= -2 ,\text{ and }c= -1 .\end{align*} Using $x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ or the Quadratic Formula, then \begin{align*}\require{cancel} x&= \dfrac{-(-2)\pm\sqrt{(-2)^2-4(4)(-1)}}{2(4)} \\\\&= \dfrac{2\pm\sqrt{4+16}}{8} \\\\&= \dfrac{2\pm\sqrt{20}}{8} \\\\&= \dfrac{2\pm\sqrt{4\cdot5}}{8} \\\\&= \dfrac{2\pm\sqrt{4}\cdot\sqrt{5}}{8} \\\\&= \dfrac{2\pm2\sqrt{5}}{8} \\\\&= \dfrac{\cancelto12\pm\cancelto12\sqrt{5}}{\cancelto48} \\\\&= \dfrac{1\pm\sqrt{5}}{4} .\end{align*} Hence, the solution set of the equation $ 8x^2-4x=2 $ is $\left\{\dfrac{1-\sqrt{5}}{4},\dfrac{1+\sqrt{5}}{4}\right\}$.
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