a,
A= \frac{2x+\sqrt{x}}{\sqrt{x}}-\frac{\sqrt{x}(\sqrt{x^{3}}+1)}{x-\sqrt{x}+1}
=\frac{\sqrt{x}(2\sqrt{x}+1)}{\sqrt{x}}-\frac{x^{2}+\sqrt{x}}{x-\sqrt{x}+1}
=2\sqrt{x}+1-\frac{\sqrt{x}(x\sqrt{x}+1)}{x-\sqrt{x}+1}
=2\sqrt{x}+1-\sqrt{x}(\sqrt{x}+1)
=2\sqrt{x}+1-x-\sqrt{x}
=-x+\sqrt{x}+1
Vậy x>0...