已知集合U={1,2,3,4,5},若A∪B=U,A∩B={3,4},且A∩(∁UB)={1,2},试写出满足上述条件的集合A和B.

问题描述:

已知集合U={1,2,3,4,5},若A∪B=U,A∩B={3,4},且A∩(∁UB)={1,2},试写出满足上述条件的集合A和B.

A∪B=U且A∩(CUB)={1,2},
所以{1,2}⊆A,3∈B,4∈B,5∈B且1∉B,2∉B;
故B={3,4,5};但A∩B≠∅,故{1,2}⊂A,
于是{1,2}⊂A⊆{1,2,3,4,5}.
即A={1,2,3}或{1,2,4}或{1,2,5}或{1,2,3,4}或{1,2,3,5}或{1,2,4,5}或{1,2,3,4,5};B={3,4,5};