Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 11 - Quadratic Functions and Equations - 11.1 Quadratic Equations - 11.1 Exercise Set - Page 707: 93


$b=\pm 18$

Work Step by Step

$x^{2}+bx+81$ By following the perfect-square trinomial rule $(A+B)^{2}=A^{2}+2AB+B^{2}$, we see that $A^{2}=x^{2}$ and $B^{2}=81$. The square roots of $A^{2}$ and $B^{2}$ are $\pm x$ and $\pm 9$. Because of the perfect-square trinomial rule, $ bx=2\cdot x\cdot B \qquad$..substitute $9$ for $B$ and divide the expression with $x$. $b=2\cdot\pm 9$ $b=\pm 18$
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