$\sum_{}^{a}(\frac{x^5}{y^3} +xy+ y^2)\ge 3(x^2+y^2+z^2) \ge (x+y+z)^2$$\Rightarrow P\ge t^2-6-12\ln t-\frac{22}{t}+\frac{6}{t^2} (t=x+y+z>0)$$t^2=12-(x^2+y^2+z^2)\le12-\frac{t^2}{3}=>0<t \le 3 $xét $f(t)=...$$f'(t)=2t^4-12t^2+22t-12=0=>t=1$ or $t=-3,....$Từ BBT...
$\sum_{}^{a}(\frac{x^5}{y^3} +xy+ y^2)\ge 3(x^2+y^2+z^2) \ge (x+y+z)^2$$\Rightarrow P\ge t^2-6-12\ln t-\frac{22}{t}+\frac{6}{t^2} (t=x+y+z>0)$$t^2=12-(x^2+y^2+z^2)\le12-\frac{t^2}{3}=>t \ge 3$xét $f(t)=...$$f'(t)=2t^4-12t^2+22t-12=0=>t=1$ or $t=-3,....$Từ BĐTVậy $f(t) \ge f(3)=\frac{-11}{3}-12\ln3$ :D :D :D
$\sum_{}^{a}(\frac{x^5}{y^3} +xy+ y^2)\ge 3(x^2+y^2+z^2) \ge (x+y+z)^2$$\Rightarrow P\ge t^2-6-12\ln t-\frac{22}{t}+\frac{6}{t^2} (t=x+y+z>0)$$t^2=12-(x^2+y^2+z^2)\le12-\frac{t^2}{3}=>
0<t \
le 3
$xét $f(t)=...$$f'(t)=2t^4-12t^2+22t-12=0=>t=1$ or $t=-3,....$Từ B
BT
...