P2=94x2+169y2+2536z2+4xy+209yz+52zx=(94x2+14z2)+(169y2+49z2)+4xy+209yz+52zx≥32xy+169yz+4xy+209yz+52zx=4(xy+yz+zx)=4Dấu bằng xảy ra $\begin{cases}z=2y=6x \\ xy+yz+zx=1 \end{cases}\Leftrightarrow \begin{cases}x=\frac1{3\sqrt3} \\ y=\frac1{\sqrt3}\\z=\frac2{\sqrt3} \end{cases}$
P2=94x2+169y2+2536z2+4xy+209yz+52zx=(94x2+14z2)+(169y2+49z2)+4xy+209yz+52zx≥32xy+169yz+4xy+209yz+52zx=4(xy+yz+zx)=4Dấu bằng xảy ra $\begin{cases}z=2y=3x \\ xy+yz+zx=1 \end{cases}$