7集的特征

CHARACTERIJATION OF 7-SETS

本文主要研究了在度量空个E中,对任意一子集A,?、A、A_-、α(A)、β(A)、α(?)、β(A_-)全不相等的充分必要条件;进而究了在拓扑空间中,任意一子集A是Kuratowski——14集的充分必要条件.

Suppoe E is a meltric space and A is a subset of E, in this paper the uecessary and sufficient condition that subset A, A°、A、A^-、α(A)、β(A)α(A°)、and β(A^-) are all different is given. In addition, the condition for a subset A of a topological space S to produce Kuratowski-14 sets is also given.