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Quotients of polynomials

Source: Indian IMOTC 2013, Team Selection Test 4, Problem 2

July 30, 2013
algebrapolynomialalgebra proposed

Problem Statement

Let n2n \ge 2 be an integer and f1(x),f2(x),,fn(x)f_1(x), f_2(x), \ldots, f_{n}(x) a sequence of polynomials with integer coefficients. One is allowed to make moves M1,M2,M_1, M_2, \ldots as follows: in the kk-th move MkM_k one chooses an element f(x)f(x) of the sequence with degree of ff at least 22 and replaces it with (f(x)f(k))/(xk)(f(x) - f(k))/(x-k). The process stops when all the elements of the sequence are of degree 11. If f1(x)=f2(x)==fn(x)=xn+1f_1(x) = f_2(x) = \cdots = f_n(x) = x^n + 1, determine whether or not it is possible to make appropriate moves such that the process stops with a sequence of nn identical polynomials of degree 1.