a: \(P=\dfrac{\sqrt{x}+1-\sqrt{x}+1-2\sqrt{x}}{2\left(x-1\right)}\)
\(=\dfrac{-2\left(\sqrt{x}-1\right)}{2\left(x-1\right)}=\dfrac{-1}{\sqrt{x}+1}\)
b: Khi x=4/9 thì \(A=\dfrac{-1}{\dfrac{2}{3}+1}=-1:\dfrac{5}{3}=-\dfrac{3}{5}\)
c: Để P=1/3 thì căn x+1=-3(loại)