Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 4 - Quadratic Functions and Equations - Chapter Review - Page 272: 81

Answer

$x=\left\{ \dfrac{1}{5}-\dfrac{2}{5}i,\dfrac{1}{5}+\dfrac{2}{5}i \right\} $

Work Step by Step

Using $ax^2+bx+c=0,$ the given equation, \begin{align*} 5x^2-2x+1=0 ,\end{align*} has $a= 5 ,$ $b= -2 ,$ and $c= 1 .$ Using the Quadratic Formula which is given by $x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a},$ then \begin{align*}\require{cancel} x&=\dfrac{-(-2)\pm\sqrt{(-2)^2-4(5)(1)}}{2(5)} \\\\&= \dfrac{2\pm\sqrt{4-20}}{10} \\\\&= \dfrac{2\pm\sqrt{-16}}{10} \\\\&= \dfrac{2\pm\sqrt{-1}\cdot\sqrt{16}}{10} \\\\&= \dfrac{2\pm\sqrt{-1}\cdot4}{10} \\\\&= \dfrac{2\pm i\cdot4}{10} \\\\&= \dfrac{2\pm 4i}{10} \\\\&= \dfrac{\cancel2^1\pm \cancel4^2i}{\cancel{10}^5} &\text{ (divide by $2$)} \\\\&= \dfrac{1\pm 2i}{5} \\\\&= \dfrac{1}{5}\pm \dfrac{2}{5}i .\end{align*} The solutions are $ x=\left\{ \dfrac{1}{5}-\dfrac{2}{5}i,\dfrac{1}{5}+\dfrac{2}{5}i \right\} .$
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