MathDB
Sum of P(x_i) are equal

Source: Own. IMO 2022 Malaysian Training Camp 1

January 29, 2022
algebrapolynomial

Problem Statement

Given a polynomial PZ[X]P\in \mathbb{Z}[X] of degree kk, show that there always exist 2d2d distinct integers x1,x2,x2dx_1, x_2, \cdots x_{2d} such that P(x1)+P(x2)+P(xd)=P(xd+1)+P(xd+2)++P(x2d)P(x_1)+P(x_2)+\cdots P(x_{d})=P(x_{d+1})+P(x_{d+2})+\cdots + P(x_{2d}) for some dk+1d\le k+1.
[Extra: Is this still true if dkd\le k? (Of course false for linear polynomials, but what about higher degree?)]