2. P=$\frac{\sqrt{z-4}}{z}+\frac{\sqrt{x-2}}{x}+\frac{\sqrt{y-3}}{y}$
có $z-4+4\geq 4\sqrt{z-4} \Rightarrow \frac{\sqrt{z-4}}{z}\leq \frac{1}{4}$
TT $\Rightarrow \frac{\sqrt{x-2}}{x} \leq \frac{1}{2\sqrt{2}} ;\frac{\sqrt{y-3}}{y}\leq\frac{1}{2\sqrt{3}} $
$\Rightarrow P\leq \frac{1}{4}+\frac{1}{2\sqrt{2}}+\frac{1}{2\sqrt{3}}$
dấu "=" $\Leftrightarrow x=4,y=6;z=8$