bạn nào giỏi toán giải hộ mình câu 3 vs ạ

$\begin{array}{l} a)A = \left( {\frac{2}{{\sqrt x - 1}} - \frac{{\sqrt x + 1}}{{x - \sqrt x }}} \right):(\frac{{x + \sqrt x }}{{\sqrt x + 1}} - \frac{{2\sqrt x - 2}}{{\sqrt x - 1}})\\ = \left[ {\frac{{2\sqrt x - (\sqrt x + 1)}}{{x - \sqrt x }}} \right]:\left[ {\frac{{\sqrt x (\sqrt x + 1)}}{{\sqrt x + 1}} - 2} \right]\\ = \frac{{\sqrt x - 1}}{{\sqrt x (\sqrt x - 1)}}:(\sqrt x - 2)\\ = \frac{1}{{\sqrt x (\sqrt x - 2)}}\\ b)A < 0 \to \sqrt x - 2 < 0 \to \sqrt x < 2 \to 0 < x < 4,x \ne 1 \end{array}$