1,Cho a,b,c là độ dài 3 cạnh của 1 tam giác .Cmr
\(\dfrac{a}{b+c}\)+\(\dfrac{b}{c+a}\)+\(\dfrac{c}{a+b}\)<2
2,Cho \(\dfrac{1}{x}\)+\(\dfrac{1}{y}\)+\(\dfrac{1}{z}\)=\(\dfrac{1}{x+y+z}\)
CMR \(\dfrac{1}{x^{2011}}\)+\(\dfrac{1}{y^{2011}}\)+\(\dfrac{1}{z^{2011}}\)=\(\dfrac{1}{x^{2011}+y^{2011}+z^{2011}}\)