a: ĐKXĐ: x>0; x<>1; x<>4
\(V=\left(\frac{1}{\sqrt{x}-1}-\frac{1}{\sqrt{x}}\right):\left(\frac{\sqrt{x}+1}{\sqrt{x}-2}-\frac{\sqrt{x}+2}{\sqrt{x}-1}\right)\)
\(=\frac{\sqrt{x}-\left(\sqrt{x}-1\right)}{\sqrt{x}\left(\sqrt{x}-1\right)}:\frac{\left(\sqrt{x}+1\right)\left(\sqrt{x}-1\right)-\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-1\right)}\)
\(=\frac{1}{\sqrt{x}\left(\sqrt{x}-1\right)}\cdot\frac{\left(\sqrt{x}-2\right)\left(\sqrt{x}-1\right)}{x-1-x+4}=\frac{\sqrt{x}-2}{3\sqrt{x}}\)
b: \(V=\frac{-1}{2}\)
=>\(\frac{\sqrt{x}-2}{3\sqrt{x}}=\frac{-1}{2}\)
=>\(-3\sqrt{x}=2\left(\sqrt{x}-2\right)=2\sqrt{x}-4\)
=>\(-5\sqrt{x}=-4\)
=>\(\sqrt{x}=\frac45\)
=>x=16/25(nhận)
