Đáp án: + Giải thích các bước giải:
$ x = 9$
$A = \dfrac{\sqrt{9} - 3}{\sqrt{9} - 2}$
$= \dfrac{3-3}{3 - 2}$
$= 0$
2)
B = $(\dfrac{\sqrt{x}}{\sqrt{x} - 1} - \dfrac{5}{\sqrt{x} + 1} + \dfrac{2}{1 - x}) . \dfrac{\sqrt{x} + 1}{2}$
B = $(\dfrac{\sqrt{x}(\sqrt{x}+1)}{x - 1} - \dfrac{5(\sqrt{x} - 1)}{x - 1} - \dfrac{2}{x - 1}) . \dfrac{\sqrt{x} + 1}{2}$
B = $\dfrac{x + \sqrt{x} - 5\sqrt{x} + 5 - 2}{(\sqrt{x} - 1)(\sqrt{x} + 1} . \dfrac{\sqrt{x} + 1}{2}$
B = $\dfrac{x - 4\sqrt{x} + 3}{(\sqrt{x} - 1)(\sqrt{x} + 1)} . \dfrac{\sqrt{x} + 1}{2}$
B = $\dfrac{(\sqrt{x} - 1)(\sqrt{x} - 3)}{(\sqrt{x} - 1)(\sqrt{x} + 1)} . \dfrac{\sqrt{x} + 1}{2}$
B = $\dfrac{\sqrt{x} - 3}{2}$
