Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 8 - Review Exercises - Page 657: 26

Answer

$\{4-\sqrt 5,4+\sqrt 5\}$

Work Step by Step

First we determine the domain of the equation: $$(-\infty,-1)\cup(-1,\infty).$$ Multiply each side by $4(x+1)$ to clear denominators: $$\begin{align*} 4(x+1)\left(\dfrac{5}{x+1}+\dfrac{x-1}{4}\right)&=4(x+1)(2)\\ 20+(x^2-1)&=8(x+1)\\ x^2+19&=8x+8. \end{align*}$$ Bring the equation to the standard form: $$\begin{align*} x^2+19-8x-8&=0\\ x^2-8x+11&=0. \end{align*}$$ Build a perfect square, then use the difference of squares to find the solutions: $$\begin{align*} (x^2-8x+16)-5&=0\\ (x-4)^2-5&=0\\ (x-4-\sqrt 5)(x-4+\sqrt 5)&=0\\ x-4-\sqrt 5=0&\text{ or }x-4+\sqrt 5=0\\ x=4+\sqrt 5&\text{ or }x=4-\sqrt 5. \end{align*}$$ Both solutions are in the domain, so the solution set of the equation is: $$\{4-\sqrt 5,4+\sqrt 5\}.$$
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