设全集I={1,2,3,···9}A,B是I的子集,若A∩B={1,2,3},就称(A,B)为好集,求好集多少个)个吗?请证明.

问题描述:

设全集I={1,2,3,···9}A,B是I的子集,若A∩B={1,2,3},就称(A,B)为好集,求好集多少个)个吗?请证明.