Source: Ukrainian Mathematical Olympiad 2021. Day 1, Problem 8.1
December 20, 2023
number theorypolynomial
Problem Statement
It is known that for some integers a2021,a2020,…,a1,a0 and any positive integer n, the expression a2021n2021+a2020n2020+…+a1n+a0
is divisible by 10. Is it necessary that each of the numbers a2021,a2020,…,a1,a0 is also divisible by 10?