第96页 - 苏科版数学补充习题八年级上下册答案

6

28

$\frac 8 {15}$

$解：原式 ={\sqrt {27×3}}$

$={\sqrt {81}}$

$=9$

$解：原式 ={\sqrt {15×{\frac {5} {3}}}}$

$={\sqrt {25}}$

$=5$

$解：原式 =3{\sqrt {7}}×({\sqrt {7}}×{\sqrt {2}})×{\sqrt {2}}$

$=(3{\sqrt {7}×{\sqrt {7}}})×({\sqrt {2}×{\sqrt {2}}})$

$=21×2$

$=42$

$解：原式 ={\sqrt {2a·{\frac {a} {2}·{a}^{2}}}}$

$={\sqrt {{a}^{4}}}$

$={a}^{2}$

$解：\sqrt {18}$

$={\sqrt {9×2}}$

$={\sqrt {9}}×{\sqrt {2}}$

$=3{\sqrt {2}}$

$解：\sqrt {27}$

$={\sqrt {9×3}}$

$={\sqrt {9}×{\sqrt {3}}}$

$=3{\sqrt {3}}$

$解：\sqrt {32}$

$={\sqrt {16×2}}$

$={\sqrt {16}}×{\sqrt {2}}$

$=4{\sqrt {2}}$

$解：\sqrt {72}$

$={\sqrt {36×2}}$

$={\sqrt {36}}×\sqrt {2}$

$=6\sqrt {2}$