olymmath

INMO 2023 Problem 2

    Suppose a0,…,a100a_{0}, \ldots, a_{100} are positive reals. Consider the following polynomial for each kk in {0,1,…,100}\{0,1, \ldots, 100\} :

    a100+kx100+100a99+kx99+a98+kx98+a97+kx97+⋯+a2+kx2+a1+kx+aka_{100+k} x^{100}+100 a_{99+k} x^{99}+a_{98+k} x^{98}+a_{97+k} x^{97}+\cdots+a_{2+k} x^{2}+a_{1+k} x+a_{k}

    where indices are taken modulo 101, i.e., a100+i=ai−1a_{100+i}=a_{i-1} for any ii in {1,2,…,100}\{1,2, \ldots, 100\}. Show that it is impossible that each of these 101 polynomials has all its roots real.

    Dataset text NuminaMath olympiads. Quoted with source.

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