Algebra 2 Common Core

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

Chapter 4 - Quadratic Functions and Equations - 4-7 The Quadratic Formula - Practice and Problem-Solving Exercises - Page 245: 18

Answer

$x=-3-\sqrt{14} \text{ and } x=-3+\sqrt{14} $

Work Step by Step

Using the properties of equality, the given equation, $ 6x-5=-x^2 ,$ is equivalent to \begin{align*} x^2+6x-5=0 \end{align*} In the equation above, $a= 1 ,$ $b= 6 ,$ and $c= -5 .$ Using the Quadratic Formula which is given by $x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a},$ then \begin{align*}\require{cancel}x&= \dfrac{-6\pm\sqrt{6^2-4(1)(-5)}}{2(1)} \\\\&= \dfrac{-6\pm\sqrt{36+20}}{2} \\\\&= \dfrac{-6\pm\sqrt{56}}{2} \\\\&= \dfrac{-6\pm\sqrt{4\cdot14}}{2} \\\\&= \dfrac{-6\pm2\sqrt{14}}{2} \\\\&= \dfrac{-\cancel6^3\pm\cancel2^1\sqrt{14}}{\cancel2^1} &\text{ (divide by $2$)} \\\\&= -3\pm\sqrt{14} \end{align*} Hence, the solutions are $ x=-3-\sqrt{14} \text{ and } x=-3+\sqrt{14} .$
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