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第127页

信息发布者：

$2\sqrt{3}$

④

$ \begin{aligned}解：原式&=\frac {\sqrt5}{2\sqrt{10}} \\ &=\frac {\sqrt2}4 \\ \end{aligned}$

$ \begin{aligned}解：原式&=\frac {3\sqrt2}{\sqrt{a}} \\ &=\frac {3\sqrt{2a}}a \\ \end{aligned}$

$ \begin{aligned}解：原式&=\frac {3\sqrt{y}}{2\sqrt{2x}} \\ &=\frac {3\sqrt{2xy}}{4x} \\ \end{aligned}$

$ \begin{aligned}解：原式&=\frac {\sqrt{3a}}{3\sqrt{6ab}} \\ &=\frac {\sqrt{3a}×\sqrt{6ab}}{3×\sqrt{6ab}×\sqrt{6ab}} \\ &=\frac {\sqrt{2b}}{6b} \\ \end{aligned}$

$ \begin{aligned}解：原式&=\frac {\sqrt{5(a-b)}}{3\sqrt{3(a+b)}} \\ &=\frac {\sqrt{5(a-b)}×\sqrt{3(a+b)}}{3×\sqrt{3(a+b)}×\sqrt{3(a+b)}} \\ &=\frac {\sqrt {15a^2-15b^2}}{9a+9b} \\ \end{aligned}$

$ \begin{aligned}解：原式&=\frac {(m-n)\sqrt{m-n}}{\sqrt{m-n}×\sqrt{m-n}} \\ &=\sqrt{m-n} \\ \end{aligned}$

$ \begin{aligned}解：原式&=9\sqrt {\frac {1}{48}}÷(-\frac 32\sqrt {\frac 94})×3\sqrt {\frac 32} \\ &=9×(-\frac 23)×3×\sqrt {\frac {1}{48}×\frac 49×\frac 32} \\ &=-18×\frac {\sqrt {2}}{12} \\ &=-\frac {3\sqrt {2}}2 \\ \end{aligned}$

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