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RMO 2017 P3

Source: RMO 2017 P3

October 8, 2017
algebraReal Roots

Problem Statement

Let P(x)=x2+x2+bP(x)=x^2+\dfrac x 2 +b and Q(x)=x2+cx+dQ(x)=x^2+cx+d be two polynomials with real coefficients such that P(x)Q(x)=Q(P(x))P(x)Q(x)=Q(P(x)) for all real xx. Find all real roots of P(Q(x))=0P(Q(x))=0.