第122页 - 江苏版启东中学作业本八年级数学（上下册）

C

D

$-a \sqrt{-a}$

$3\sqrt2$

$ \begin{aligned} 解：原式&=\sqrt{5(x^2-2x+1)} \\ &=\sqrt{5(x-1)^2} \\ &=\sqrt5(1-x) \\ \end{aligned}$

$ \begin{aligned}解：原式&= \sqrt{16x^2(x^2+2)} \\ &=4 \sqrt{x^2+2}|x| \\ \end{aligned}$

$ \begin{aligned} 解：原式&=2a^3b·a\sqrt{b}×3×\frac{1}{b}\sqrt{ab}·\frac{1}{2}\sqrt a \\ &=3a^4\sqrt{a^2b^2} \\ &= 3a^5b \\ \end{aligned}$

$ $

$ \begin{aligned} 原式&=-\frac{9}{y}\sqrt{xy^5·x^3y·\frac{x}{y^5}} \\ &=-\frac{9}{y}. \sqrt{x^5y} \\ &=-\frac{9x^2}{y}\sqrt{xy} \\ \end{aligned}$

$ $

$ \begin{aligned}解：原式&= \sqrt{a^2.a} \\ &= \sqrt{a^3} \\ \end{aligned}$

$ \begin{aligned} 解：原式&= \sqrt{a^2·\frac{1}{a}} \\ &=\sqrt{a} \\ \end{aligned}$

$ \begin{aligned}解：原式&=-\sqrt{a^2·(-a)} \\ &=- \sqrt{-a^3} \\ \end{aligned}$

$ \begin{aligned}原式&=- \sqrt{3^2×3} \\ &=- \sqrt{27} \\ \end{aligned}$

$ \begin{aligned} 解：原式&=\sqrt{(-x)^2·(-x)} \\ &=\sqrt{-x^3} \\ \end{aligned}$

$ \begin{aligned}解：原式&=-(a-2) \sqrt{\frac{1}{a-2}} \\ &=- \sqrt{(a-2)^2·\frac{1}{a-2}} \\ &=-\sqrt{a-2} \\ \end{aligned}$

（更多请查看作业精灵详解）

$\sqrt{n+\frac{n}{n^2-1}}=n\sqrt{\frac{n}{(n^2-1)}}$