\(P=\frac{a}{\sqrt{a}-1}-\frac{2a-2\sqrt{a}}{a-\sqrt{a}}\)
\(=\frac{a}{\sqrt{a}-1}-\frac{2\sqrt{a}\left(\sqrt{a}-1\right)}{\sqrt{a}\left(\sqrt{a}-1\right)}\)
\(=\frac{a}{\sqrt{a}-1}-2\)
\(=\frac{a-2\sqrt{a}+1}{\sqrt{a}-1}=\frac{\left(\sqrt{a}-1\right)^2}{\sqrt{a}-1}\)
\(=\sqrt{a}-1\)