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 246: 55

Answer

$x\approx-7.47 \text{ and } x\approx1.47$

Work Step by Step

Using the properties of equality, the given equation, $ x^2=11-6x ,$ is equivalent to \begin{align*} x^2+6x-11=0 \end{align*} In the equation above, $a= 1 ,$ $b= 6 ,$ and $c= -11 .$ 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)(-11)}}{2(1)} \\\\&= \dfrac{-6\pm\sqrt{36+44}}{2} \\\\&= \dfrac{-6\pm\sqrt{80}}{2} \\\\&= \dfrac{-6\pm\sqrt{16\cdot5}}{2} \\\\&= \dfrac{-6\pm4\sqrt{5}}{2} \\\\&= \dfrac{-\cancel6^3\pm\cancel4^2\sqrt{5}}{\cancel2^1} &\text{ (divide by $2$)} \\\\&= \dfrac{-3\pm2\sqrt{5}}{1} \\\\&= -3\pm2\sqrt{5} \end{align*} \begin{array}{lcl} &\Rightarrow -3-2\sqrt{5} &\text{ OR }& -3+2\sqrt{5} \\\\& \approx-7.47 && \approx1.47 \end{array} Hence, the solutions are $ x\approx-7.47 \text{ and } x\approx1.47 .$
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