Đáp án:
$\displaystyle B=\frac{1-x}{\sqrt{x}}$
Giải thích các bước giải:
$\displaystyle \begin{array}{{>{\displaystyle}l}} B=\left(\frac{x}{4} +\frac{1}{4x} -2.\frac{1}{4}\right) .\frac{\left(\sqrt{x} -1\right)^{2} -\left(\sqrt{x} +1\right)^{2}}{\left(\sqrt{x} -1\right)\left(\sqrt{x} +1\right)} .\\ =\frac{x^{2} +1-2x}{4x} .\frac{x-2\sqrt{x} +1-x-2\sqrt{x} -1}{\left(\sqrt{x} -1\right)\left(\sqrt{x} +1\right)}\\ =\frac{( x-1)^{2}}{4x} .\frac{-4\sqrt{x}}{\left(\sqrt{x} -1\right)\left(\sqrt{x} +1\right)} =\frac{1-x}{\sqrt{x}} \end{array}$
