a: \(=\dfrac{\sqrt{x}+2+x-\sqrt{x}+1}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-1\right)}:\dfrac{x-1-x+\sqrt{x}+4}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-1\right)}\)
\(=\dfrac{x+3}{\sqrt{x}+3}\)
c: Để P nguyên thì \(x-9+12⋮\sqrt{x}+3\)
=>\(\sqrt{x}+3\in\left\{3;4;6;12\right\}\)
=>\(x\in\left\{0;9;81\right\}\)