1)Cho a,b,c>0 thỏa mãn a+b+c=3.CMR
$\frac{a^2}{a+2b^2}+\frac{b^2}{b+2c^2}+\frac{c^2}{c+2a^2}\geq 1$
2) Cho a,b,c,d>0 thỏa mãn a+b+c+d=4.CMR
$\frac{a}{1+b^2c}+\frac{b}{1+c^2d}+\frac{c}{1+d^2a}+\frac{d}{1+a^2b}\geq 2$
3) Cho a,b,c>0 thỏa mãn abc=1.CMR
$\sqrt{\frac{1}{1+8a}}+\sqrt{\frac{1}{1+8b}}+\sqrt{\frac{1}{1+8c}}\geq 1$