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