MathDB
Polynomial and inequality

Source: VMO 2021

December 26, 2020
algebra unsolvedinequalities

Problem Statement

Let the polynomial P(x)=a21x21+a20x20++a1x+a0P(x)=a_{21}x^{21}+a_{20}x^{20}+\cdots +a_1x+a_0 where 1011ai20211011\leq a_i\leq 2021 for all i=0,1,2,...,21.i=0,1,2,...,21. Given that P(x)P(x) has an integer root and there exists an positive real numbercc such that ak+2akc|a_{k+2}-a_k|\leq c for all k=0,1,...,19.k=0,1,...,19.
a) Prove that P(x)P(x) has an only integer root.
b) Prove that k=010(a2k+1a2k)2440c2.\sum_{k=0}^{10}(a_{2k+1}-a_{2k})^2\leq 440c^2.