Cho a,b,c > 0. CMR [tex]\frac{a^2}{b^5}+\frac{b^2}{c^5}+\frac{c^2}{a^5}\geq \frac{1}{b^3}+\frac{1}{c^3}+\frac{1}{a^3}[/tex]
[tex]\frac{a^2}{b^5}+\frac{a^2}{b^5}+\frac{a^2}{b^5}+\frac{1}{a^3}+\frac{1}{a^3}\geq \frac{5}{b^3}[/tex]
Tương tự [tex]\Rightarrow 3\sum \frac{a^2}{b^5}+2\sum \frac{1}{a^3}\geq 5\sum \frac{1}{a^3}\Rightarrow \sum \frac{a^2}{b^5}\geq \sum \frac{1}{a^3}[/tex] (đpcm)