\(B=\left(\frac{1}{\sqrt{x}\left(\sqrt{x}+1\right)}-\frac{1}{\sqrt{x}+1}\right).\frac{\left(\sqrt{x}+1\right)^2}{\sqrt{x}-1}\)
\(B=\frac{1-\sqrt{x}}{\sqrt{x}\left(\sqrt{x}+1\right)}.\frac{\left(\sqrt{x}+1\right)^2}{\sqrt{x}-1}\)
\(B=\frac{-\sqrt{x}-1}{\sqrt{x}}\). Vậy ....