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: 23

Answer

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

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. $\displaystyle \frac{x^2+2x-3}{3x^2-7x-6} \gt 0$ $f(x)=\displaystyle \frac{(x+3)(x-1)}{(x-3)(3x+2)} \gt 0$ 2. The cut points are: $\displaystyle \displaystyle \frac{(x+3)(x-1)}{(x-3)(3x+2)} = 0$ $x=-3$ or $x=-\frac{2}{3}$ 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, $\begin{array}{llll} Intervals: & a=test.v. & f(a),signs & f(a) \gt 0 ? \\ & & \displaystyle \displaystyle \frac{(a+3)(a-1)}{(a-3)(3a+2)} & \\ (-\infty,-3) & -5 & \frac{(-)(-)}{(-)(-)}=(+) & T\\ (-3, -\frac{2}{3}) & -2 & \frac{(+)(-)}{(-)(-)}=(-) & F\\ ( -\frac{2}{3}, 1) & 0& \frac{(+)(-)}{(-)(+)}=(+) & T\\ (1, 3) & 2 & \frac{(+)(+)}{(-)(+)}=(-) & F\\ (3,\infty) & 10 & \frac{(+)(+)}{(+)(+)}=(+) & T\\ \end{array}$ 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: $(-\infty,-3) \cup\left( -\frac{2}{3}, 1\right) \cup (3,\infty)$
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