第136页 - 经纶学典学霸八年级数学上下册【江苏国标】

A

B

C

$\frac{4\sqrt {3} }{3}$

$\frac{\sqrt {6} }{2}$

$\frac{5\sqrt {6} }{4}$

$4\sqrt {6}\ $

$\frac{8\sqrt {6} }{3}$

$解:原式=\frac{2\sqrt{3x}}{3}$

$解:原式=\frac{\sqrt {6ab}}{4a²}$

$ \begin{aligned}解:原式&= \sqrt{\frac{4}{3}×\frac {3}{7}×\frac {5}{7}} \\ &=\sqrt{\frac{20}{7²}} \\ &=\frac{2\sqrt {5} }{7}. \\ \end{aligned}$

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

$ \begin{aligned}解:原式&=\sqrt {18}÷ \sqrt{84×\frac {2}{7}} \\ &=\sqrt {18} ÷\sqrt {24}\ \\ &= \sqrt{\frac{18}{24}}= \sqrt{\frac{3}{4}} =\frac{\sqrt {3} }{2}. \\ \end{aligned}$

$ \begin{aligned}解:原式&=8x² \sqrt{xy}÷\sqrt {\frac {x^{3} }{9y}}×(-\sqrt {\frac {y^{2} }{x}} ) \\ &=-8x² \sqrt{xy·\frac{9y}{x^{3} }·\frac {y^{2} }{x}} \\ &=-8x²\sqrt {\frac {9y^{4} }{x^{3} }}\ \\ &=-8x²·\frac{3y²\sqrt{x}}{x²} \\ &=-24y²\sqrt{x}. \\ \end{aligned}$

$解:原式=\frac{\sqrt {3} }{6}$

$解:原式=\frac{3\sqrt {5} }{5}$