Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 1 - Section 1.8 - Inequalities - 1.8 Exercises - Page 89: 53

Answer

The solution is $(-\infty,-2)\cup(-2,4)$ The graph is:

Work Step by Step

$(x-4)(x+2)^{2}\lt0$ Begin immediately by finding the intervals, because all nonzero terms are on one side of the inequality and the nonzero side is given in factored form. The factors are $x-4$ and $(x+2)^{2}$. Set them equal to $0$ and solve for $x$: $x-4=0$ $x=4$ $(x+2)^{2}=0$ $x+2=0$ $x=-2$ The factors are zero when $x=4,-2$. These two numbers divide the real line into the following intervals: $(-\infty,-2)$ $,$ $(-2,4)$ $,$ $(4,\infty)$ Elaborate a diagram, using test points to determine the sign of each factor in each interval: (refer to the attached image below) It can be seen from the diagram that the inequality is satisfied only on the intervals $(-\infty,-2)$ and $(-2,4)$. Also, the inequality involves $\lt$ so the endpoints don't satisfy the inequality. The solution is $(-\infty,-2)\cup(-2,4)$
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