Toàn bài khó
Dễ thấy $0<x_1 < x_2 < ... < x_{2014}$
$\Rightarrow x_{2014}^n < x_1^n + x_2^n + ... + x_{2014}^n < 2014. x_{2014}^n$
$\Rightarrow x_{2014} < \sqrt[n]{x_1^n + x_2^n + ... + x_{2014}^n }< \sqrt[n]{2014} .x_{2014}\ (*)$
Ta có $\dfrac{k}{(k+1)!}=\dfrac{1}{k!}-\dfrac{1}{(k+1)!} \Rightarrow \sum \limits_{n=1}^k \dfrac{n}{(n+1)!}=1-\dfrac{1}{(k+1)!}$
$\Rightarrow x_{2014}=1-\dfrac{1}{2015!}$
Ta có $(*) $
$1-\dfrac{1}{2015!}< \sqrt[n]{x_1^n + x_2^n + ... + x_{2014}^n }< \sqrt[n]{2014} (1-\dfrac{1}{2015!})<1-\dfrac{1}{2015!}$
Xong nha