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IMO 2004 — Complete Shortlist Question 1

IMO Shortlist · IMO 2004 — Complete Shortlist

Question 1

Let $ n \geq 3 $ be an integer and $ t_1, t_2, \ldots, t_n $ positive real numbers such that

$$ n^{2}+1 \gt \left(t_{1}+t_{2}+\cdots+t_{n}\right)\left(\frac{1}{t_{1}}+\frac{1}{t_{2}}+\cdots+\frac{1}{t_{n}}\right). $$

Show that $t_i, t_j, t_k$ are the side lengths of a triangle for all $i, j, k$ with $1 \leq i \lt j \lt k \leq n$.