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: 21

Answer

$(-\infty,-1-\sqrt 3) \cup[0, -1+\sqrt 3)$

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