[nooonuii]

ข้อ 4 ครับ

จาก 3(ab+bc+ca) ฃ (a+b+c)² จะได้

\[ \large{ 3[(xy)^2(yz)^2+(yz)^2(zx)^2+(zx)^2(xy)^2] \leq [(xy)^2+(yz)^2+(zx)^2]^2 } \]

\[ \large{ 3(xyz)^2[x^2+y^2+z^2] \leq [(xy)^2+(yz)^2+(zx)^2]^2} \]

\[ \large{ \frac{xy}{z} + \frac{yz}{x} + \frac{zx}{y} \geq 5\sqrt{3} } \]