N
ntp_9x98


Cho $x,y,z$ là ba số dương . Chứng minh
[TEX]\frac{1}{x^2(y+z)^2}+\frac{1}{y^2(x+z)^2}+\frac{1}{z^2(x+y)^2}\geq \frac{9}{4xyz(x+y+z)}[/TEX]
[TEX]\frac{1}{x^2(y+z)^2}+\frac{1}{y^2(x+z)^2}+\frac{1}{z^2(x+y)^2}\geq \frac{9}{4xyz(x+y+z)}[/TEX]
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