\(B=\left(\dfrac{\sqrt{x}+1}{\sqrt{x}-1}-\dfrac{\sqrt{x}-1}{\sqrt{x}+1}\right):\left(\dfrac{\sqrt{x}}{x+\sqrt{x}}-\dfrac{\sqrt{x}}{1-\sqrt{x}}+\dfrac{1}{x-1}\right)\left(dkxd:x>0,x\ne1\right)\)
\(=\left(\dfrac{\left(\sqrt{x}+1\right)^2-\left(\sqrt{x}-1\right)^2}{x-1}\right):\left(\dfrac{\sqrt{x}}{\sqrt{x}\left(\sqrt{x}+1\right)}-\dfrac{\sqrt{x}}{\sqrt{x}-1}+\dfrac{1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\right)\)
\(=\left(\dfrac{\left(\sqrt{x}+1-\sqrt{x}+1\right)\left(\sqrt{x}+1+\sqrt{x}-1\right)}{x-1}\right):\left(\dfrac{\sqrt{x}\left(\sqrt{x}-1\right)-x\left(\sqrt{x}+1\right)+\sqrt{x}}{\sqrt{x}\left(x-1\right)}\right)\)
\(=\left(\dfrac{4\sqrt{x}}{x-1}\right):\left(\dfrac{x-\sqrt{x}-x\sqrt{x}-x+\sqrt{x}}{\sqrt{x}\left(x-1\right)}\right)\)
\(=\dfrac{4\sqrt{x}}{x-1}.\dfrac{\sqrt{x}\left(x-1\right)}{-x\sqrt{x}}\)
\(=-\dfrac{4\sqrt{x}}{x}\)
Vậy \(B=-\dfrac{4\sqrt{x}}{x}\) với \(x>0,x\ne1\)
