Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 8 - Radical Functions - 8.4 Solving Radical Equations - 8.4 Exercises - Page 655: 88

Answer

$x=-7.5 $, $x= 3$

Work Step by Step

Given \begin{equation} \frac{5}{x+2}+\frac{2 x}{x-7}=\frac{10}{x^2-5 x-14}. \end{equation} Factor the denominator on the right hand side. \begin{equation} \begin{aligned} x^2-5 x-14&=0 \\ x^2+2x-7x-14&= 0\\ x(x+2)-7(x+2)&= 0\\ (x+2)(x-7)&= 0. \end{aligned} \end{equation} Rewrite the solution: \begin{equation} \begin{aligned} \frac{5}{x+2}+\frac{2 x}{x-7}&=\frac{10}{x^2-5 x-14}\\ \frac{5}{(x+2)}+\frac{2 x}{(x-7)}&=\frac{10}{(x+2)(x-7)}\\ \left( \frac{5}{(x+2)}+\frac{2 x}{(x-7)} \right)\cdot (x+2)(x-7) & =\frac{10(x+2)(x-7)}{(x+2)(x-7)} \\ 2x(x+2)+5(x-7)& =10\\ 2x^2+4x+5x-35-10&= 0\\ 2x^2+9x-45&= 0. \end{aligned} \end{equation} We solve the quadratic equation: \begin{equation} \begin{aligned} a & =2, b=9, c=-45 \\ x & =\frac{-b \pm \sqrt{b^2-4 a c}}{2 a} \\ x & =\frac{-9 \pm \sqrt{9^2-4 \cdot 2(-45)}}{2 \cdot 2}\\ & =\frac{-9\pm 21}{4} \\ \Longrightarrow x& =\frac{-9 + 21}{4}\\ &=3\\ x& =\frac{-9 -21}{4}\\ &=-7.5\\ \end{aligned} \end{equation} The solution is $x=-7.5 $ , $x= 3$.
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