P263. Saudi Arabia IMO TST
Source:
August 3, 2018
saSequences
Problem Statement
Let be an integer and let
\begin{align*}
x_1,x_2, \ldots, x_n
\end{align*}
be distinct integers. Prove that
\begin{align*}
(x_1 - x_2)^2 + (x_2 - x_3)^2 + \ldots + (x_n - x_1)^2 \geq 4n - 6.
\end{align*}