第127页 - 江苏版启东中学作业本八年级数学（上下册）

A

B

C

$\frac{1}{2}$

$3≤x＜4$

2

8

1或2

$ \begin{aligned}解：原式&= \sqrt{100×2} \\ &=10\sqrt{2} \\ \end{aligned}$

$ \begin{aligned}解：原式&= \sqrt{\frac{7}{5}} \\ &=\frac{\sqrt{35}}{5} \\ \end{aligned}$

$ \begin{aligned} 解：原式&=\frac{\sqrt{2}}{\sqrt3} \\ &=\frac{\sqrt{6}}{3} \\ \end{aligned}$

$ $

$ \begin{aligned}解：原式&=-\sqrt{\frac{20}{3}} \\ &=-\frac{2\sqrt{15}}{3} \\ \end{aligned}$

$ \begin{aligned} 解：原式&=a·\frac{1}{\sqrt a} \\ &=\frac{a\sqrt{a}}{\sqrt a·\sqrt a} \\ &=\sqrt a \\ \end{aligned}$

$ \begin{aligned}解：原式&=6×\sqrt{\frac{6}{16}} \\ &=6×\frac{\sqrt{6}}{4} \\ &=\frac{3\sqrt6}{2} \\ \end{aligned}$

$ \begin{aligned} 解：原式&=\sqrt{25a^2}×\sqrt{2b} \\ &=5a\sqrt{2b} \\ \end{aligned}$

$ \begin{aligned}解：原式&=\frac{n}{m}× \sqrt{\frac{mn}{n^2}} \\ &=-\frac{\sqrt{mn}}{m} \\ \end{aligned}$