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IMO Shortlist 2012, Algebra 7

Source: IMO Shortlist 2012, Algebra 7

July 29, 2013
functionlinear algebraalgebrapolynomialIMO Shortlist

Problem Statement

We say that a function f:RkRf:\mathbb{R}^k \rightarrow \mathbb{R} is a metapolynomial if, for some positive integers mm and nn, it can be represented in the form f(x1,,xk)=maxi=1,,mminj=1,,nPi,j(x1,,xk),f(x_1,\cdots , x_k )=\max_{i=1,\cdots , m} \min_{j=1,\cdots , n}P_{i,j}(x_1,\cdots , x_k), where Pi,jP_{i,j} are multivariate polynomials. Prove that the product of two metapolynomials is also a metapolynomial.