We have n>2 non-zero integers such that each one of them is divisible by the sum of the other n−1 numbers. Prove that the sum of all the given numbers is zero.
Problem
Source: VI Caucasus Mathematical Olympiad
Tags: number theory
Kamran011
14.03.2021 14:14
here it is
hakN
24.04.2021 23:34
Let a1,a2,…,an be the given numbers and let S=∑ni=1ai. We have S−ai∣ai⟹S−ai∣S for all i. Let ki=SS−ai for ki∈Z. We have ai=S⋅(ki−1)ki. So taking the sum we have, S=∑ni=1ai=S⋅∑ni=1(1−1ki). If S≠0, then we have ∑ni=11ki=n−1⟹k1=k2=⋯=kn−2=1 and kn−1=kn=2. But this is clearly a contradiction since then a1=a2=⋯=an−2=0. So S=0 as desired. ◼ @below 10=6+2+2∤
triangle112
05.05.2021 19:12
(6,2,2,2)?
triangle112
06.05.2021 00:48
@above oooh ok i see, thanks
Asilbek_Abduqayumov18-06
20.01.2022 13:02
nice problem but easy to P3