$\frac{a}{b}+\frac{b}{c}+\frac{c}{a}+2\sqrt{2}.\frac{ab+bc+ca}{a^2+b^2+c^2}\geq (1+\sqrt{2})^2$
Bai2:
$\left ( 1+\frac{4a^2}{(b+c)^2} \right ).\left ( 1+\frac{4b^2}{(c+a)^2} \right ).\left ( 1+\frac{4c^2}{(a+b)^2} \right )\geq 8$
- Poseidont, WhjteShadow và duc12116 thích