a: \(P=\left(\dfrac{x-1}{2\sqrt{x}}\right)^2\cdot\dfrac{x-2\sqrt{x}+1-x-2\sqrt{x}-1}{x-1}\)
\(=\dfrac{\left(x-1\right)^2}{4x}\cdot\dfrac{-4\sqrt{x}}{x-1}=\dfrac{-\left(x-1\right)}{\sqrt{x}}\)
b: Để P>0 thì -(x-1)>0
=>x-1<0
=>0<x<1
c: Để P=-2 thì \(-\left(x-1\right)=-2\sqrt{x}\)
=>\(x-1-2\sqrt{x}=0\)
=>căn x=1+căn 2
=>x=3+2 căn 2