Answer
9i
Work Step by Step
$\sqrt(-81)=\sqrt (81\times-1)=\sqrt 81\times\sqrt -1=9\times i=9i$
We know that $\sqrt -1=i$, because $i^{2}=-1$.
Intermediate Algebra (6th Edition)
by Martin-Gay, Elayn
Published by
Pearson
ISBN 10:
0321785045
ISBN 13:
978-0-32178-504-6
Chapter 7 - Section 7.7 - Complex Numbers - Exercise Set - Page 463: 1
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