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: 35

Answer

$-8 \text{ and } -7$

Work Step by Step

Let $x$ be the integer. Then $x+1$ is the other integer. The conditions of the problem translate to \begin{array}{l}\require{cancel} \dfrac{1}{x}+\dfrac{1}{x+1}=-\dfrac{15}{56} .\end{array} Using the properties of equality, the equation above is equivalent to \begin{array}{l}\require{cancel} 56x(x+1)\left(\dfrac{1}{x}+\dfrac{1}{x+1}\right)=\left(-\dfrac{15}{56}\right)56x(x+1) \\\\ 56(x+1)(1)+56x(1)=x(x+1)(-15) \\\\ 56x+56+56x=-15x^2-15x \\\\ 15x^2+(56x+56x+15x)+56=0 \\\\ 15x^2+127x+56=0 \\\\ (x+8)(15x+7)=0 .\end{array} Equating each factor to $0$ (Zero Product Property) and solving for the variable, then the solutions are $x=\left\{ -8,-\dfrac{7}{15}\right\}.$ Since $x$ is an integer then $x=-8$ is the only acceptable answer. Hence, the integers are $ -8 \text{ and } -7 .$
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