MathDB
Problem 2 of Third round

Source: IX International Festival of Young Mathematicians Sozopol, Theme for 10-12 grade

September 22, 2018
number theory

Problem Statement

The set of numbers (p,a,b,c)(p, a, b, c) of positive integers is called Sozopolian when:
* p is an odd prime number
* aa, bb and cc are different and
* ab+1ab + 1, bc+1bc + 1 and ca+1ca + 1 are a multiple of pp.
a) Prove that each Sozopolian set satisfies the inequality p+2a+b+c3p+2 \leq \frac{a+b+c}{3}
b) Find all numbers pp for which there exist a Sozopolian set for which the equality of the upper inequation is met.