College Algebra 7th Edition

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

Chapter 3, Polynomial and Rational Functions - Section 3.7 - Polynomial and Rational Inequalities - 3.7 Exercises - Page 352: 30

Answer

Solution set: $(-\infty, -2) \cup \left[-\frac{1}{3}, 1\right) \cup(3, \infty) $

Work Step by Step

1. Express the inequality in the form $f(x)<0, f(x)>0, f(x)\leq 0$, or $f(x)\geq 0,$ where $f$ is a Rational function. $\displaystyle \frac{1}{x-3} +\frac{1}{x+2} \geq \frac{2x}{x^2+x-2}$, $\displaystyle \frac{1}{x-3} +\frac{1}{x+2}- \frac{2x}{(x+2)(x-1) }\geq 0$, $\displaystyle \frac{3x+1}{(x-3)(x+2)(x-1)}\geq 0$, $f(x)=\displaystyle \frac{3x+1}{(x-3)(x+2)(x-1)}\geq 0$, 2.The cut points are: $\displaystyle \frac{3x+1}{(x-3)(x+2)(x-1)}=$ $x=-2$ or $x=-\frac{1}{3}$ or $x=1$ or $x=3$ 3. Make a table or diagram: use the test values to make a table or diagram of the sign of each factor in each interval. 4. Test each interval's sign of $f(x)$ with a test value, $\begin{array}{llll} Intervals: & a=test.v. & f(a),signs & f(a) \geq 0 ? \\ & & \displaystyle \displaystyle \frac{3a+1}{(a-3)(a+2)(a-1)} & \\ (-\infty,-2) & -5 & \frac{(-)}{(-)(-)(-)}=(+) & T\\ (-2, -\frac{1}{3}) & -1 & \frac{(-)}{(-)(+)(-)}=(-) & F\\ (-\frac{1}{3}, 1) & 0 & \frac{(+)}{(-)(+)(-)}=(+) & T\\ (1, 3) & 2 & \frac{(+)}{(-)(+)(+)}=(-) & F\\ (3,\infty) & 5 & \frac{(+)}{(+)(+)(+)}=(+) & T\\ \end{array}$ 5. Write the solution set, selecting the interval or intervals that satisfy the given inequality. If the inequality involves $\leq$ or $\geq$, include the boundary points. Solution set: $(-\infty, -2) \cup \left[-\frac{1}{3}, 1\right) \cup(3, \infty) $
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