Sean $2n$ reales positivos $a_1,a_2,...,a_{2n}$. Sean $s = a_1 + a_3 +...+ a_{2n-1}$ , $t = a_2 + a_4 + ... + a_{2n}$ , y $x_k = a_k + a_{k+1} + ... + a_{k+n-1}$ (los índices se toman módulo $2n$ ). Demuestra que $$\frac{s}{x_1}+\frac{t}{x_2}+\frac{s}{x_3}+\frac{t}{x_4}+...+\frac{s}{x_{2n-1}}+\frac{t}{x_{2n}}>\frac{2n^2}{n+1}$$