IMO 2020 Shortlist A7
Let n and k be positive integers. Prove that for a1,...,an P r1,2k s one has n ÿ i“1 ai a a2 1 ... a2 i ď 4 ? kn. (Iran)
Category: Algebra
Problem
Let n and k be positive integers. Prove that for a1,...,an P r1,2k
s one has
n ÿ
i“1
ai
a
a2
1 ... a2
i
ď 4
?
kn.
(Iran)