College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 4 - Section 4.5 - Inequalities involving Quadratic Functions - 4.5 Assess Your Understanding - Page 314: 32

Answer

a. $x=\frac{1\pm \sqrt 5}{2},$ b. $x=-2$ or $x=3$ c. $x=-\frac{5}{2},$ d. $\frac{1- \sqrt 5}{2}

Work Step by Step

$f(x)=-x^2-x+1,$ $g(x)=-x^2+x+6,$ a. $-x^2-x+1=0,$ Solving the quadratic equation using the quadratic formula, $x=\frac{-b\pm \sqrt {b^2-4ac}}{2a},$ In this case, $x=\frac{1\pm \sqrt {(-1)^2-4(-1)(1)}}{2(-1)}=\frac{1\pm \sqrt 5}{2},$ b. $-x^2+x+6=0,$ $-x^2-2x+3x+6=0,$ $-x(x+2)+3(x+2)=0,$ $(-x+3)(x+2)=0,$ $x=-2$ or $x=3$ c. $-x^2-x+1=-x^2+x+6,$ $-2x-5=0,$ $x=-\frac{5}{2},$ d. $-x^2-x+1>0,$ $\frac{1- \sqrt 5}{2}-x^2+x+6,$ $-2x-5>0,$ $x<-\frac{5}{2}$ g. $-x^2-x+1\geq1,$ $-x^2-x\geq0,$ $-x(x+1)\geq0,$ $-1\leq x\leq 0$
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