#### Answer

$-\sqrt 105$

#### Work Step by Step

$\sqrt -7\times\sqrt -15=i\sqrt 7\times i\sqrt 15=i^{2}\sqrt (7\times15)=i^{2}\sqrt 105=-1\times\sqrt 105=-\sqrt 105$
We know that $\sqrt -1=i$, because $i^{2}=-1$.

Published by
Pearson

ISBN 10:
0321969359

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

$-\sqrt 105$

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