B
bigbang195


[TEX]a,b,c[/TEX] không âm sao cho [TEX]ab+bc+ac=1[/TEX]. Chứng minh
[TEX]\frac{3ab+1}{a+b}+\frac{3bc+1}{b+c}+\frac{3ac+1}{a+c} \ge 4[/TEX]
[TEX]\frac{3ab+1}{a+b}+\frac{3bc+1}{b+c}+\frac{3ac+1}{a+c} \ge 4[/TEX]