Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 6 - Section 6.6 - Rational Equations and Problem Solving - Exercise Set - Page 388: 36

Answer

$9 \text{ and } 11$

Work Step by Step

Let $x$ be the odd integer. Then $x+2$ is the other odd integer. The conditions of the problem translate to \begin{array}{l}\require{cancel} \dfrac{1}{x}+\dfrac{1}{x+2}=\dfrac{20}{99} .\end{array} Using the properties of equality, the equation above is equivalent to \begin{array}{l}\require{cancel} 99x(x+2)\left(\dfrac{1}{x}+\dfrac{1}{x+2}\right)=\left(\dfrac{20}{99}\right)99x(x+2) \\\\ 99(x+2)(1)+99x(1)=x(x+2)(20) \\\\ 99x+198+99x=20x^2+40x \\\\ -20x^2+(99x+99x-40x)+198=0 \\\\ -20x^2+158x+198=0 \\\\ \dfrac{-20x^2+158x+198}{-2}=\dfrac{0}{-2} \\\\ 10x^2-79x-99=0 \\\\ (x-9)(10x+11)=0 .\end{array} Equating each factor to $0$ (Zero Product Property) and solving for the variable, then the solutions are $x=\left\{ 9,-\dfrac{11}{10}\right\}.$ Since $x$ is an odd integer then $x=9$ is the only acceptable answer. Hence, the odd integers are $ 9 \text{ and } 11 .$
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