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: 44

Answer

$x\approx-2.90 \text{ and } x\approx1.90 $

Work Step by Step

Using the properties of equality, the given equation, $ 4x^2+4x=22 ,$ is equivalent to \begin{align*} 4x^2+4x-22&=0 \\\\ \dfrac{4x^2+4x-22}{2}&=\dfrac{0}{2} \\\\ 2x^2+2x-11&=0 \end{align*} In the equation above, $a= 2 ,$ $b= 2 ,$ 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{-2\pm\sqrt{2^2-4(2)(-11)}}{2(2)} \\\\&= \dfrac{-2\pm\sqrt{4+88}}{4} \\\\&= \dfrac{-2\pm\sqrt{92}}{4} \\\\&= \dfrac{-2\pm\sqrt{4\cdot23}}{4} \\\\&= \dfrac{-2\pm2\sqrt{23}}{4} \\\\&= \dfrac{-\cancel2^1\pm\cancel2^1\sqrt{23}}{\cancel4^2} &\text{ (divide by $2$)} \\\\&= \dfrac{-1\pm\sqrt{23}}{2} \end{align*} \begin{array}{lcl} &\Rightarrow \dfrac{-1-\sqrt{23}}{2} &\text{ OR }& \dfrac{-1+\sqrt{23}}{2} \\\\& \approx-2.90 && \approx1.90 \end{array} Hence, the solutions are$ x\approx-2.90 \text{ and } x\approx1.90 .$
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