ĐKXĐ: x>0 và x<>1
\(A=\left(\dfrac{\sqrt{x}-1}{\sqrt{x}+1}-\dfrac{\sqrt{x}+1}{\sqrt{x}-1}\right)\cdot\left(\dfrac{1}{2\sqrt{x}}-\dfrac{\sqrt{x}}{2}\right)\)
\(=\dfrac{\left(\sqrt{x}-1\right)^2-\left(\sqrt{x}+1\right)^2}{x-1}\cdot\dfrac{1-x}{2\sqrt{x}}\)
\(=\dfrac{x-2\sqrt{x}+1-x-2\sqrt{x}-1}{-2\sqrt{x}}=2\)
A=1-căn x
=>\(1-\sqrt{x}=2\)
=>\(\sqrt{x}=-1\)(vô lý)
=>Chọn A