a)=(\(\dfrac{1.\sqrt{x}}{\sqrt{x}.\left(\sqrt{x}-1\right)}\)-\(\dfrac{2}{\sqrt{x}.\left(\sqrt{x}-1\right)}\)) : \(\dfrac{\sqrt{x}-2}{\left(\sqrt{x}-1\right)^2}\)
=\(\dfrac{\sqrt{x}-2}{\sqrt{x}.\left(\sqrt{x}-1\right)}\). \(\dfrac{\left(\sqrt{x}-1\right)^2}{\sqrt{x}-2}\)
=\(\dfrac{\sqrt{x}-1}{\sqrt{x}}\)
b) Vì \(\sqrt{x}\) > 0
\(\Rightarrow\) Để P < 0 thì \(\sqrt{x}-1\) < 0
\(\Leftrightarrow\) \(\sqrt{x}\) < 1
\(\Rightarrow\)x < 1
Vậy để P < 0 thì x < 1