a: Ta có: P=AB
\(=\left(\dfrac{5\sqrt{x}}{\sqrt{x}-2}+\dfrac{\sqrt{x}-1}{\sqrt{x}+2}-\dfrac{5x+2}{x-4}\right)\cdot\dfrac{x-4}{x+2\sqrt{x}}\)
\(=\dfrac{5x+10\sqrt{x}+x-3\sqrt{x}+2-5x-2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\cdot\dfrac{\sqrt{x}-2}{\sqrt{x}}\)
\(=\dfrac{x+7\sqrt{x}}{\sqrt{x}+2}\cdot\dfrac{1}{\sqrt{x}}\)
\(=\dfrac{\sqrt{x}+7}{\sqrt{x}+2}\)