College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 1, Equations and Graphs - Section 1.7 - Solving Inequalities - 1.7 Exercises - Page 148: 75

Answer

$(-\infty,-2)\cup(7,\infty)$

Work Step by Step

$(\frac{a}{b})^n=\frac{a^n}{b^n}$, $\left(\frac{1}{x^2-5x-14}\right)^{1/2}=\frac{1}{\sqrt{x^2-5x-14}},$ solving for trinomial, $x^2-5x-14=x^2+2x-7x-14=x(x+2)-7(x+2)=(x-7)(x+2)=0,$ thus, $x=7$ or $x=-2$ Since Domain of square root is greater than or equal to zero and the denominator cannot be zero, we check our interval as follows. Therefore, $\begin{array}{lll} Intervals & (x-7)(x+2)& (x-7)(x+2)>0?\\ (-\infty, -2) & (-)(-)=(+)& True\\ (-2, 7) & (-)(+)=(-)& False\\ (7,\infty)&(+)(+)=(+)& True \end{array}$ Thus, The solution set: $(-\infty,-2)\cup(7,\infty)$
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