Câu hỏi 67
Cho $a,b,c\in[0,1]$. Chứng minh
$$\frac1{1+a+b}+\frac1{1+b+c}+\frac1{1+c+a}+a+b+c\le3+\frac13(ab+bc+ca).$$
$$\frac1{1+a+b}+\frac1{1+b+c}+\frac1{1+c+a}+a+b+c\le3+\frac13(ab+bc+ca).$$
MathNet 2012 Câu hỏi 67
Math Olympiad Vault · MathNet 2012