gọi m=min {$x_{i}$} và M=max{$x_{i}$}
cmr $x_{1}^{2}+x_{2}^{2}+...+x_{n}^{2}\leq -n.m.M$
2) Cho $x_{1},x_{2},...x_{n}$ >0
gọi m=min{$x_{i}$} và M=max{$x_{i}$}
cmr $n^{2}\leq (x_{1}+x_{2}+..+x_{n})(\frac{1}{x_{1}}+\frac{1}{x_{2}}+...+\frac{1}{x_{n}})\leq n^{2}.\frac{(m+M)^{2}}{4mM}$
Edited by iloveyou123, 02-11-2012 - 11:31.
