#### Answer

$-i$

#### Work Step by Step

$-\sqrt-1=-(\sqrt (-1\times1))=-(\sqrt -1\times\sqrt 1)=-(i\times1)=-(i)=-i$
We know that $\sqrt -1=i$, because $i^{2}=-1$.

Published by
Pearson

ISBN 10:
0321969359

ISBN 13:
978-0-32196-935-4

$-i$

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