3:
a: \(P=\dfrac{3x+3-2x+6\sqrt{x}-x-3\sqrt{x}}{x-9}:\dfrac{2\sqrt{x}-2-\sqrt{x}+3}{\sqrt{x}-3}\)
\(=\dfrac{3\sqrt{x}+3}{x-9}\cdot\dfrac{\sqrt{x}-3}{\sqrt{x}+1}=\dfrac{3}{\sqrt{x}+3}\)
b: Khi x=20-6căn 11 thì \(P=\dfrac{3}{\sqrt{11}-3+3}=\dfrac{3}{\sqrt{11}}\)
c: P>1/2
=>P-1/2>0
=>\(\dfrac{3}{\sqrt{x}+3}-\dfrac{1}{2}>0\)
=>6-căn x-3>0
=>3-căn x>0
=>0<x<9