#### Answer

$\{-9,9\}$

#### Work Step by Step

Since $(
-9
)^2=
81
$ and $
9
^2=
81
$, the square roots of $
81
$ are $
\{-9,9\}
$.

Published by
Pearson

ISBN 10:
0-32184-874-8

ISBN 13:
978-0-32184-874-1

$\{-9,9\}$

Since $(
-9
)^2=
81
$ and $
9
^2=
81
$, the square roots of $
81
$ are $
\{-9,9\}
$.

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