MathDB
There exists a permutation

Source: IMO Longlist 1989, Problem 69

September 18, 2008
algebrapolynomialcombinatorics unsolvedcombinatorics

Problem Statement

Let k k and s s be positive integers. For sets of real numbers {α1,α2,,αs} \{\alpha_1, \alpha_2, \ldots , \alpha_s\} and {β1,β2,,βs} \{\beta_1, \beta_2, \ldots, \beta_s\} 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 sk, s \leq k, then there exists a permutation π \pi of {1,2,,s} \{1, 2, \ldots , s\} such that \beta_i \equal{} \alpha_{\pi(i)}   \forall i \equal{} 1,2, \ldots, s.