Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 1 - Equations and Inequalities - 1.4 Quadratic Equations - 1.4 Exercises - Page 121: 14

Answer

$\left\{-4,2\right\}$

Work Step by Step

RECALL: A trinomial of the form $x^2+bx+c$ can be factored if there are integers $d$ and $e$ such that $c=de$ and $b=d+e$. The trinomial's factored form will be: $x^2+bx+c=(x+d)(x+e)$ The given trinomial has $b=2$ and $c=-8$. Note that $-8=4(-2)$ and $2= 4-2$. This means that $d=4$ and $e=-2$ The given equation maybe written as: $(x+4)(x-2) =0$ Use the Zero-Factor Property by equating each factor to zero. Then, solve each equation to obtain: $\begin{array}{ccc} &x+4 = 0 &\text{ or } &x-2=0 \\&x=-4 &\text{ or } &x=2 \end{array}$ Thus, the solution set is $\left\{-4, 2\right\}$.
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