三个子群的并是子群的充要条件

An Equivalent Condition of Subgroup for the Union of Three Subgroups

设G是群,H1,H2,H3是G的子群.本文给出了H1∪H2∪H3≤G的充要条件.

Let G be a group and H1,H2,H3 be subgroups of G. In this paper,we give an equivalent condition for H1∪ H2∪ H3≤ G.