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: 35

Answer

$\left\{ \dfrac{-1-i\sqrt{23}}{4},\dfrac{-1+i\sqrt{23}}{4} \right\}$

Work Step by Step

The standard form of the given equation, $ \dfrac{2}{5}y^2+\dfrac{1}{5}y+\dfrac{3}{5}=0 ,$ is \begin{array}{l}\require{cancel} 5\left( \dfrac{2}{5}y^2+\dfrac{1}{5}y+\dfrac{3}{5} \right)=(0)5 \\\\ 2y^2+y+3=0 .\end{array} Using $\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ (or the Quadratic Formula), the solutions of the quadratic equation, $ 2y^2+y+3=0 ,$ are \begin{array}{l}\require{cancel} \dfrac{-(1)\pm\sqrt{(1)^2-4(2)(3)}}{2(2)} \\\\= \dfrac{-1\pm\sqrt{1-24}}{4} \\\\= \dfrac{-1\pm\sqrt{-23}}{4} \\\\= \dfrac{-1\pm i\sqrt{23}}{4} .\end{array} Hence, the solutions are $ \left\{ \dfrac{-1-i\sqrt{23}}{4},\dfrac{-1+i\sqrt{23}}{4} \right\} .$
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