1. Cho $a,b,c>0$ CMR: $\frac{a^{2}}{b^{2}+c^{2}}+\frac{b^{2}}{c^{2}+a^{2}}+\frac{c^{2}}{a^{2}+b^{2}}$$\geq \frac{a}{b+c}+\frac{b}{c+a}+\frac{c}{a+b}$
2.Cho $a^{2}+b^{2}+c^{2}=1$.CMR:$2.\left ( a+1 \right ).\left (b+1 \right ).\left ( c+1 \right )\geq abc$
- khanghaxuan và Pham Quoc Thang thích