a: ĐKXĐ: x>0; x<>4
b: \(A=\dfrac{4+4\sqrt{x}+x-4+4\sqrt{x}-x+4x}{4-x}:\dfrac{2\sqrt{x}-\sqrt{x}-3}{2\sqrt{x}-x}\)
\(=\dfrac{4\sqrt{x}\left(\sqrt{x}+2\right)}{4-x}\cdot\dfrac{\sqrt{x}\left(2-\sqrt{x}\right)}{\sqrt{x}-3}=\dfrac{4x}{\sqrt{x}-3}\)
c: \(A-1=\dfrac{4x-\sqrt{x}+3}{\sqrt{x}-3}< 0\)
=>căn x-3<0
=>0<x<9 và x<>4