Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 8 - Section 8.2 - Solving Quadratic Equations by the Quadratic Formula - Exercise Set - Page 492: 40

Answer

$\left\{ \dfrac{3-\sqrt{5}}{4},\dfrac{3+\sqrt{5}}{4} \right\}$

Work Step by Step

The standard form of the given equation, $ \left( p-\dfrac{1}{2} \right)^2=\dfrac{p}{2} ,$ is \begin{array}{l}\require{cancel} (p)^2+2(p)\left(-\dfrac{1}{2}\right)+\left(-\dfrac{1}{2}\right)^2=\dfrac{p}{2} \\\\ p^2-p+\dfrac{1}{4}=\dfrac{p}{2} \\\\ 4\left( p^2-p+\dfrac{1}{4} \right)=\left(\dfrac{p}{2}\right)(4) \\\\ 4(p^2)+4(-p)+1(1)=p(2) \\\\ 4p^2-4p+1=2p \\\\ 4p^2+(-4p-2p)+1=0 \\\\ 4p^2-6p+1=0 .\end{array} Using $\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ (or the Quadratic Formula), the solutions of the quadratic equation, $ 4p^2-6p+1=0 ,$ are \begin{array}{l}\require{cancel} \dfrac{-(-6)\pm\sqrt{(-6)^2-4(4)(1)}}{2(4)} \\\\= \dfrac{6\pm\sqrt{36-16}}{8} \\\\= \dfrac{6\pm\sqrt{20}}{8} \\\\= \dfrac{6\pm\sqrt{4\cdot5}}{8} \\\\= \dfrac{6\pm\sqrt{(2)^2\cdot5}}{8} \\\\= \dfrac{6\pm2\sqrt{5}}{8} \\\\= \dfrac{2(3\pm\sqrt{5})}{8} \\\\= \dfrac{\cancel{2}(3\pm\sqrt{5})}{\cancel{2}\cdot4} \\\\= \dfrac{3\pm\sqrt{5}}{4} .\end{array} Hence, the solutions are $ \left\{ \dfrac{3-\sqrt{5}}{4},\dfrac{3+\sqrt{5}}{4} \right\} .$
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