#### Answer

$2\sqrt 5$

#### Work Step by Step

$\sqrt 20=\sqrt (4\times5)=\sqrt 4\times\sqrt 5=2\sqrt 5$
We know that $\sqrt 4=2$, because $2^{2}=4$.

Published by
Pearson

ISBN 10:
0321969359

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

$2\sqrt 5$

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