B
banhbaocua1


cho x,y,z khác 0 và \frac{1}{x}+\frac{1}{y}+\frac{1}{z}=\frac{1}{a+b+c}
CMR: \frac{1}{x^2011}+\frac{1}{y^2011}+\frac{1}{z^2011}=\frac{1}{x^2011+y^2011+z^2011}
CMR: \frac{1}{x^2011}+\frac{1}{y^2011}+\frac{1}{z^2011}=\frac{1}{x^2011+y^2011+z^2011}