Precalculus (6th Edition) Blitzer

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

Chapter 2 - Cumulative Review Exercises - Page 435: 12

Answer

The value of x for the inequality $3{{x}^{2}}>2x+5$ is $\left( -\infty ,-1 \right)\cup \left( \frac{5}{3},\infty \right)$.

Work Step by Step

  Solve: $\begin{align} & 3{{x}^{2}}>2x+5 \\ & 3{{x}^{2}}-2x-5>0 \\ & 3{{x}^{2}}+3x-5x-5>0 \\ & \left( x+1 \right)\left( 3x-5 \right)>0 \end{align}$ As the inequality is "greater than", either both of the factors should be positive or both should be negative. Thus, apply the above condition to obtain: $x\in \left( -\infty ,-1 \right)\cup \left( \frac{5}{3},\infty \right)$ The value of x for the inequality $3{{x}^{2}}>2x+5$ is $\left( -\infty ,-1 \right)\cup \left( \frac{5}{3},\infty \right)$.
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