第128页 - 经纶学典新课时作业八年级数学上下册【江苏国标】

$\sqrt{ab}$

≥0

$\sqrt{b}$

≥0

能开得尽方

B

C

D

6

6a

5

$ \begin{aligned}解:原式&=\sqrt{27×\frac {1}{3}} \\ &=\sqrt{9} \\ &=3 \\ \end{aligned}$

$ \begin{aligned}解:原式&=2\sqrt{xy·\frac {1}{y}} \\ &=2\sqrt{x} \\ \end{aligned}$

$ \begin{aligned} 解:原式&=\sqrt{6}×2\sqrt{2}×(-2\sqrt{3}) \\ &=-24 \\ \end{aligned}$

$ 解:原式=4\sqrt{2}$

$ \begin{aligned} 解:原式&=\sqrt{0.25}×\sqrt{0.36} \\ &=0.5×0.6 \\ &=0.3 \\ \end{aligned}$

C

$解:∵a≥0，b≥0$

$ \begin{aligned} ∴原式&=\sqrt{(3ab)^2·a} \\ &=3ab\sqrt{a} \\ \end{aligned}$