Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 11 - Quadratic Functions and Equations - 11.3 Studying Solutions of Quadratic Equations - 11.3 Exercise Set - Page 718: 52

Answer

$16{{x}^{2}}-40x-8=0$

Work Step by Step

$\frac{5}{4}-\frac{\sqrt{33}}{4}\ \text{and }\frac{5}{4}+\frac{\sqrt{33}}{4}$ It can be expressed as: $x=\frac{5}{4}+\frac{\sqrt{33}}{4}$ and $x=\frac{5}{4}-\frac{\sqrt{33}}{4}$ $\begin{align} & x-\left( \frac{5}{4}+\frac{\sqrt{33}}{4} \right)=0 \\ & \left( x-\frac{5}{4} \right)-\frac{\sqrt{33}}{4}=0 \end{align}$ Or, $\begin{align} & x-\left( \frac{5}{4}-\frac{\sqrt{33}}{4} \right)=0 \\ & \left( x-\frac{5}{4} \right)+\frac{\sqrt{33}}{4}=0 \\ \end{align}$ Apply the zero-product property: $\left( \left( x-\frac{5}{4} \right)-\frac{\sqrt{33}}{4} \right)\left( \left( x-\frac{5}{4} \right)+\frac{\sqrt{33}}{4} \right)=0$ $\begin{align} & \left( \left( x-\frac{5}{4} \right)-\frac{\sqrt{33}}{4} \right)\left( \left( x-\frac{5}{4} \right)+\frac{\sqrt{33}}{4} \right)=0 \\ & \left( x-\frac{5}{4} \right)\left( x-\frac{5}{4} \right)+\frac{\sqrt{33}}{4}\left( x-\frac{5}{4} \right)-\frac{\sqrt{33}}{4}\left( x-\frac{5}{4} \right)-{{\left( \frac{\sqrt{33}}{4} \right)}^{2}}=0 \end{align}$ Combine the like terms: ${{\left( x-\frac{5}{4} \right)}^{2}}-{{\left( \frac{\sqrt{33}}{4} \right)}^{2}}=0$ Apply the formula, ${{\left( a+b \right)}^{2}}={{a}^{2}}+{{b}^{2}}+2ab$ $\begin{align} & {{\left( x-\frac{5}{4} \right)}^{2}}-{{\left( \frac{\sqrt{33}}{4} \right)}^{2}}=0 \\ & {{x}^{2}}+\frac{25}{16}-2x\cdot \frac{5}{4}-\frac{33}{16}=0 \\ & {{x}^{2}}-\frac{5x}{2}+\frac{25-33}{16}=0 \\ & {{x}^{2}}-\frac{5x}{2}-\frac{8}{16}=0 \end{align}$ Multiply the equation by $16$ to clear the fraction, $\begin{align} & 16\left( {{x}^{2}}-\frac{5x}{2}-\frac{8}{16} \right)=0 \\ & 16{{x}^{2}}-40x-8=0 \end{align}$
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