a: \(P=\dfrac{a-4-5-\sqrt{a}-3}{\left(\sqrt{a}+3\right)\left(\sqrt{a}-2\right)}=\dfrac{\left(\sqrt{a}-4\right)\left(\sqrt{a}+3\right)}{\left(\sqrt{a}+3\right)\left(\sqrt{a}-2\right)}\)
\(=\dfrac{\sqrt{a}-4}{\sqrt{a}-2}\)
b: \(P-1=\dfrac{\sqrt{a}-4-\sqrt{a}+2}{\sqrt{a}-2}=\dfrac{-2}{\sqrt{a}-2}< 0\)
Để P-1<0 thì căn a-2>0
=>a>4
c: Để P nguyên thì \(\sqrt{a}-2\in\left\{1;-1;2;-2\right\}\)
hay \(a\in\left\{9;1;16;0\right\}\)