a,\(\left(\dfrac{2}{\sqrt{x}-2}+\dfrac{\sqrt{x}-1}{2\sqrt{x}-x}\right):\left(\dfrac{\sqrt{x}+2}{\sqrt{x}}-\dfrac{\sqrt{x}-1}{\sqrt{x}-2}\right)\)
\(=\dfrac{2\sqrt{x}-\sqrt{x}+1}{\sqrt{x}\left(\sqrt{x}-2\right)}:\dfrac{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)-\sqrt{x}\left(\sqrt{x}-1\right)}{\sqrt{x}\left(\sqrt{x}-2\right)}\)
\(=\dfrac{\sqrt{x}+1}{\sqrt{x}\left(\sqrt{x}-2\right)}.\dfrac{\sqrt{x}\left(\sqrt{x}-2\right)}{x-4-x+\sqrt{x}}\)
\(=\dfrac{\sqrt{x}+1}{\sqrt{x}-4}\)
b,\(\left(\dfrac{3\sqrt{x}}{\sqrt{x}+2}+\dfrac{\sqrt{x}}{\sqrt{x}-2}+\dfrac{3x-5\sqrt{x}}{4-x}\right):\left(\dfrac{2\sqrt{x}-1}{\sqrt{x}-2}-1\right)\)
\(=\dfrac{3\sqrt{x}\left(\sqrt{x}-2\right)+\sqrt{x}\left(\sqrt{x}+2\right)-\left(3x-5\sqrt{x}\right)}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}:\dfrac{2\sqrt{x}-1-\left(\sqrt{x}-2\right)}{\sqrt{x}-2}\)
\(=\dfrac{3x-6\sqrt{x}+x+2\sqrt{x}-3x+5\sqrt{x}}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}:\dfrac{\sqrt{x}+1}{\sqrt{x}-2}\)
\(=\dfrac{x+\sqrt{x}}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}.\dfrac{\sqrt{x}-2}{\sqrt{x}+1}\)
\(=\dfrac{\sqrt{x}\left(\sqrt{x}+1\right)}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}.\dfrac{\sqrt{x}-2}{\sqrt{x}+1}\)
\(=\dfrac{\sqrt{x}}{\sqrt{x}+2}\)
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