Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 2 - Section 2.7 - Polynomial and Rational Inequalities - Exercise Set - Page 412: 14

Answer

See below:

Work Step by Step

Simplify the provided inequality by subtracting 1 from both sides, $6{{x}^{2}}+x-1>0$ The boundary points of the given inequality will be calculated by equating $f\left( x \right)$ to 0 as $6{{x}^{2}}+x-1>0$ Thus, $\begin{align} & 6{{x}^{2}}+3x-2x-1=0 \\ & 3x\left( 2x+1 \right)-1\left( 2x+1 \right)=0 \\ & \left( 3x-1 \right)\left( 2x+1 \right)=0 \end{align}$ Hence, $x=\frac{1}{3},x=-\frac{1}{2}$ From the above number line, the boundary points divide the number line into three parts as, $\left( -\infty ,-\frac{1}{2} \right)\text{,}\left( -\frac{1}{2},\frac{1}{3} \right)\text{ and }\left( \frac{1}{3},\infty \right)$. Now, one test value within each interval is chosen and f is evaluated at that number. As can be observed, for both intervals $\left( -\infty ,-\frac{1}{2} \right)\text{ and }\left( \frac{1}{3},\infty \right)$ , the function is positive. And, for interval $\left( -\frac{1}{2},\frac{1}{3} \right)$ , the function is negative. And, the points $-\frac{1}{2}\text{ and }\frac{1}{3}$ are not included in the solution because inequality is strict, that is, it does not include the equality sign. Thus, the solution set in the interval notation will be $\left( -\infty ,-\frac{1}{2}, \right)\cup \left( \frac{1}{3},\infty \right)$.
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