a: Khi x=9 thì \(A=\dfrac{1}{\sqrt{x}+1}=\dfrac{1}{3+1}=\dfrac{1}{4}\)
b: \(P=\dfrac{1}{\sqrt{x}+1}:\dfrac{\sqrt{x}+1+x}{\sqrt{x}\left(\sqrt{x}+1\right)}\)
\(=\dfrac{\sqrt{x}}{x+\sqrt{x}+1}\)
c: Để A/B=1/3 thì P=1/3
\(\Leftrightarrow3\sqrt{x}=x+\sqrt{x}+1\)
\(\Leftrightarrow x-2\sqrt{x}+1=0\)
=>x=1(nhận)