Answer
$3m\sqrt 2$
Work Step by Step
$\sqrt (18m^{2})=\sqrt (9\times m^{2}\times2)=\sqrt 9\times\sqrt m^{2}\times\sqrt 2=3m\sqrt 2$
We know that $\sqrt 9=3$, because $3^{2}=9$.
We know that $\sqrt m^{2}=m$, because $(m)^{2}=m^{2}$.
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