MathDB
Putnam 1962 A6

Source: Putnam 1962

May 15, 2022
PutnamSetsrational number

Problem Statement

Let SS be a set of rational numbers such that whenever aa and bb are members of SS, so are abab and a+ba+b, and having the property that for every rational number rr exactly one of the following three statements is true: r∈S,    −r∈S,    r=0.r\in S,\;\; -r\in S,\;\;r =0. Prove that SS is the set of all positive rational numbers.
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