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MathNet 2016-part-04 — 184 problems (EN–VI) Question 162

Math Olympiad Vault · MathNet 2016-part-04 — 184 problems (EN–VI)

Question 162

Let $n \geq 3$ and $x_{1}, x_{2}, \ldots, x_{n}$ be $n$ distinct integers. Prove that
$$
\left(x_{1}-x_{2}\right)^{2}+\left(x_{2}-x_{3}\right)^{2}+\ldots+\left(x_{n}-x_{1}\right)^{2} \geq 4 n-6 .
$$