第116页

信息发布者:
$解:原式=3\sqrt {3}×\frac {1}{\sqrt {3}}$
= $3$
$ 解:原式=\sqrt {7}×3\sqrt {7}$
=$21$
$解:原式=\sqrt {36×5}$
= $6\sqrt{5}$
$解:原式=\sqrt {225×2}$
= $15\sqrt{2}$
$解:原式=\sqrt {9x^{2}y^{2}×y}$
= $3xy\sqrt{y}$
$解:原式=\sqrt {a^{2}(a^{2}+b^{2})}$
= $a\sqrt{a^2 + b^2}$
$\mathrm{C}$
$\mathrm{B}$
$8\sqrt{2}$
$-a\sqrt{-a}$