Answer
$81$
Work Step by Step
$x^2+18x+c$
Compare it with $ax^2+bx+c$, we have $b=18$
For perfect-square trinormal add $(\frac{b}{2})^2$Plug $b=18$ to complete the square.
$c=(\frac{81}{2})^2=(9)^2=81$
Algebra 1: Common Core (15th Edition)
by Charles, Randall I.
Published by
Prentice Hall
ISBN 10:
0133281140
ISBN 13:
978-0-13328-114-9
Chapter 9 - Quadratic Functions and Equations - 9-5 Completing the Square - Practice and Problem-Solving Exercises - Page 579: 7
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