Đáp án:
$\displaystyle \frac{\sqrt{x} -1}{x-\sqrt{x} +1}$
Giải thích các bước giải:
$\displaystyle \begin{array}{{>{\displaystyle}l}} \frac{1}{\sqrt{x} +1} -\frac{3}{x\sqrt{x} +1} +\frac{1}{x-\sqrt{x} +1}\\ DK:\ x\geqslant 0\\ =\frac{x-\sqrt{x} +1-3+\sqrt{x} +1}{\left( x-\sqrt{x} +1\right)\left(\sqrt{x} +1\right)}\\ =\frac{x-1}{\left( x-\sqrt{x} +1\right)\left(\sqrt{x} +1\right)}\\ =\frac{\sqrt{x} -1}{x-\sqrt{x} +1} \end{array}$
