There exists a permutation
Source: IMO Longlist 1989, Problem 69
September 18, 2008
algebrapolynomialcombinatorics unsolvedcombinatorics
Problem Statement
Let and be positive integers. For sets of real numbers and that satisfy
\sum^s_{i\equal{}1} \alpha^j_i \equal{} \sum^s_{i\equal{}1} \beta^j_i \forall j \equal{} \{1,2 \ldots, k\}
we write \{\alpha_1, \alpha_2, \ldots , \alpha_s\} \overset{k}{\equal{}} \{\beta_1, \beta_2, \ldots , \beta_s\}.
Prove that if \{\alpha_1, \alpha_2, \ldots , \alpha_s\} \overset{k}{\equal{}} \{\beta_1, \beta_2, \ldots , \beta_s\} and then there exists a permutation of such that
\beta_i \equal{} \alpha_{\pi(i)} \forall i \equal{} 1,2, \ldots, s.