Cho $a,b,c$ không âm sao cho $c(a-b) \neq 0$.Chứng minh rằng:
$$\sum \frac{a^3}{(b+c)^3}+\frac{8(a+b)^3(b+c)^3(c+a)^3}{(ac-bc)^2(a+b+c)^5}\geq 4$$
$\sum \frac{a^3}{(b+c)^3}+\frac{8\prod (a+b)^3}{(ac-bc)^2(a+b+c)^5}\geq 4$
Started By longatk08, 10-12-2015 - 23:11
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