Solved and Unsolved Problems

[摘要] The column Solved and Unsolved Problems will continue presenting six proposed problems and two open problems, as has been doneover recent years. The set of proposed and open problems in each issue will be devoted to a specific field of mathematics. In every issuefeaturing this column, solutions will be presented to the proposedproblems from the previous issue along with the names of solvers.Possible progress toward the solution of any of the open problemsproposed in this column will also be featured. The goal of the Solvedand Unsolved Problems column is to provide a series of intriguingproposed problems and open problems ranging over several areasof mathematics. Effort will also be made to present problems of aninterdisciplinary flavour.