Đại 9 Cực trị

N

noinhobinhyen

$x^2+y^2+z^2 \geq xy+xz+yz = 12$

$3(x^4+y^4+x^4) \geq (x^2+y^2+z^2)^2 \geq 12^2=144$

$\Rightarrow P \geq 48$

$minP=48 \Leftrightarrow x=y=z=2$
 
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