#### 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.
$c=(\frac{81}{2})^2=(9)^2=81$

Published by
Prentice Hall

ISBN 10:
0133281140

ISBN 13:
978-0-13328-114-9

$81$

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