a: ĐKXĐ: x>=0; x<>1
b: \(P=\dfrac{3+\sqrt{x}-1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\cdot\dfrac{\sqrt{x}+1}{1}=\dfrac{\sqrt{x}+2}{\sqrt{x}-1}\)
c: Để \(P=\dfrac{5}{4}\) thì \(\dfrac{\sqrt{x}+2}{\sqrt{x}-1}=\dfrac{5}{4}\)
\(\Leftrightarrow5\sqrt{x}-5=4\sqrt{x}+8\)
hay x=169