第112页 - 苏科版数学补充习题八年级上下册答案

${\frac {3} {2}}{\sqrt {2}}$

$30\sqrt {2}$

3

$21-4{\sqrt {5}}$

$2{\sqrt {10}}+4{\sqrt {5}}$

$-3a$

$-{\frac {\sqrt {5}} {2}}$

$8或-8$

$解：原式 =({\frac {2} {3}×{\frac {3} {4}}})×({\sqrt {6}×{\sqrt {24}}})$

$={\frac {1} {2}}×12$

$=6$

$解：原式 =(12{\sqrt {3}-6{\sqrt {3}}})÷{\sqrt {3}}$

$=6{\sqrt {3}}÷{\sqrt {3}}$

$=6$

$解：原式 =6{\sqrt {3}}÷({\sqrt {3}-2{\sqrt {3}}})$

$=6{\sqrt {3}}÷(-{\sqrt {3}})$

$=-6$

$解：原式 ={\sqrt {10}}×3{\sqrt {\frac {2} {5}}}-{\sqrt {10}×{\sqrt {\frac {5} {2}}}}$

$=3×{\sqrt {10×{\frac {2} {5}}}}-{\sqrt {10×{\frac {5} {2}}}}$

$=3×2-5$

$=1$