Problem

Source: Belarusian-Iranian 3rd friendly competition

Tags: algebra, inequalities



Given $n \geq 2$ positive real numbers $x_1 \leq x_2 \leq \ldots \leq x_n$ satisfying the equalities $$x_1+x_2+\ldots+x_n=4n$$$$\frac{1}{x_1}+\frac{1}{x_2}+\ldots+\frac{1}{x_n}=n$$Prove that $\frac{x_n}{x_1} \geq 7+4\sqrt{3}$