IMO Shortlist 2004 problem A1
Dodao/la:
arhiva2. travnja 2012. Let
be an integer. Let
,
, ...,
be positive real numbers such that
.
Show that
,
,
are side lengths of a triangle for all
,
,
with
.
%V0
Let $n \geq 3$ be an integer. Let $t_1$, $t_2$, ..., $t_n$ be positive real numbers such that
$n^2 + 1 > \left( t_1 + t_2 + ... + t_n \right) \left( \frac{1}{t_1} + \frac{1}{t_2} + ... + \frac{1}{t_n} \right)$.
Show that $t_i$, $t_j$, $t_k$ are side lengths of a triangle for all $i$, $j$, $k$ with $1 \leq i < j < k \leq n$.
Izvor: Međunarodna matematička olimpijada, shortlist 2004