Rút gọn:
$3\sqrt{8}-\sqrt{50}-\sqrt{(\sqrt{2}-1)^2}$
$=3.2\sqrt{2}-5\sqrt{2}-\sqrt{2}+1$
$=6\sqrt{2}-5\sqrt{2}-\sqrt{2}+1$
$=1$
Khử mẫu:
a, `sqrt{\frac{2}{5}}`
`=\frac{sqrt{2}.\sqrt{5}}{5}`
`=\frac{\sqrt{10}}{5}`
b, `\sqrt{\frac{7}{12}}`
`=\frac{\sqrt{7}.\sqrt{12}}{12}`
`=\frac{2\sqrt{21}}{12}`
c, `\sqrt{\frac{5}{18ab^2}}` $(a>0;b\neq0)$
`=\frac{\sqrt{5}}{3\sqrt{2a}b}`
`=\frac{\sqrt{10a}}{6ab}`.
