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: 39

Answer

$\left\{ -1-i\sqrt{3},-1+i\sqrt{3} \right\}$

Work Step by Step

The standard form of the given equation, $ (n-2)^2=2n ,$ is \begin{array}{l}\require{cancel} (n)^2-2(n)(-2)+(-2)^2=2n \\\\ n^2+4n+4=2n \\\\ n^2+4n-2n+4=0 \\\\ n^2+2n+4=0 .\end{array} Using $\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ (or the Quadratic Formula), the solutions of the quadratic equation, $ n^2+2n+4=0 ,$ are \begin{array}{l}\require{cancel} \dfrac{-(2)\pm\sqrt{(2)^2-4(1)(4)}}{2(1)} \\\\= \dfrac{-2\pm\sqrt{4-16}}{2} \\\\= \dfrac{-2\pm\sqrt{-12}}{2} \\\\= \dfrac{-2\pm\sqrt{-1}\sqrt{12}}{2} \\\\= \dfrac{-2\pm i\sqrt{4\cdot3}}{2} \\\\= \dfrac{-2\pm i\sqrt{(2)^2\cdot3}}{2} \\\\= \dfrac{-2\pm 2i\sqrt{3}}{2} \\\\= \dfrac{2(-1\pm i\sqrt{3})}{2} \\\\= \dfrac{\cancel{2}(-1\pm i\sqrt{3})}{\cancel{2}} \\\\= -1\pm i\sqrt{3} .\end{array} Hence, the solutions are $ \left\{ -1-i\sqrt{3},-1+i\sqrt{3} \right\} .$
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