ĐKXĐ: x > 0 và x # 1
[tex](\frac{1}{1-\sqrt{x}}- \frac{1}{1+ \sqrt{x}}).\frac{x-1}{\sqrt{x}}[/tex]
= [tex](\frac{1+\sqrt{x}}{1-x}- \frac{1-\sqrt{x}}{1-x}).\frac{x-1}{\sqrt{x}}[/tex]
= [tex]\frac{1+\sqrt{x}-1+\sqrt{x}}{1-x}.\frac{x-1}{\sqrt{x}}[/tex]
=[tex]\frac{2\sqrt{x}}{1-x}.\frac{x-1}{\sqrt{x}}[/tex]
= [tex]\frac{-2\sqrt{x}}{x-1}. \frac{x-1}{\sqrt{x}}[/tex]
= -2