Precalculus (6th Edition) Blitzer

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

Chapter 4 - Section 4.2 - Trigonometric Functions: The Unit Circle - Exercise Set - Page 550: 106

Answer

The solution of the given inequality is $x\in \left( -\infty ,1 \right)\cup \left( 3,\infty \right)$.

Work Step by Step

The inequality can be solved as follows: $\begin{align} & {{x}^{2}}-4x>-3 \\ & {{x}^{2}}-4x+3>0 \end{align}$ Now, apply the method of factorization: $\begin{align} & {{x}^{2}}-3x-x+3>0 \\ & x\left( x-3 \right)-1\left( x-3 \right)>0 \\ & \left( x-1 \right)\left( x-3 \right)>0 \end{align}$ The zeros of the above inequality are 1 and 3. Now, check the different values of x in three regions on the number line system: For $x<1$ , choose any number in this region; suppose $x=0.5$. $\left( 0.5-1 \right)\left( 0.5-3 \right)=1.25$ In this region, the result is positive, which means that in this region the graph is positive. Thus, the region $x<1$ is satisfied by the inequality. For $13$, choose any number in this region; suppose $x=4$. $\left( 4-1 \right)\left( 4-3 \right)=3$ In this region, the result is positive, which means that in this region the graph is positive. Thus, the region $x>3$ is satisfied by the inequality. Therefore, the solution is $x\in \left( -\infty ,1 \right)\cup \left( 3,\infty \right)$.
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