Đáp án: 1) $2-\sqrt{5}$
2) $\frac{\sqrt{50}-\sqrt{2}}{2}$
d) $\frac{8\sqrt{b}}{3b}$
e) $\frac{6a+2a\sqrt{a}}{9-a}$
Giải thích các bước giải:
1) $\frac{2\sqrt{3}-\sqrt{15}}{\sqrt{3}}$
$=\frac{\sqrt{3}(2\sqrt{3}-\sqrt{15})}{3}$
$=\frac{2.3-\sqrt{45}}{3}$
$=\frac{2.3-3.\sqrt{5}}{3}$
$=2-\sqrt{5}$
2) $\frac{4-4\sqrt{5}}{\sqrt{2}-\sqrt{10}}$
$=\frac{(\sqrt{2}+\sqrt{10})(4-4\sqrt{5})}{2-10}$
$=\frac{4\sqrt{2}-4\sqrt{10}+4\sqrt{10}-4\sqrt{50}}{-8}$
$=\frac{\sqrt{50}-\sqrt{2}}{2}$
d) $\frac{8}{3\sqrt{b}}$ ($b>0$)
$=\frac{8\sqrt{b}}{3b}$
e) $\frac{2a}{3-\sqrt{a}}$ ($a≥0;a\neq9$)
$=\frac{2a(3+\sqrt{a})}{9-a}$
$=\frac{6a+2a\sqrt{a}}{9-a}$
