写出满足{3,4}真包含于P包含于{0,1,2,3,4}的所有集合P我要的是思路,怎么解的

Question

写出满足{3,4}真包含于P包含于{0,1,2,3,4}的所有集合P
我要的是思路,怎么解的

Answer 1

｛3,4｝真包含于P,则P除了有元素3,4外,还有别的元素
P包含于{0,1,2,3,4},则P的元素只能在0,1,2,3,4中选取.
因此P除了包含3,4,还需在{0,1,2}中任取1~3个元素组成,则共有2^3-1=7种
即：
{3,4,0},{3,4,1},{3,4,2}
{3,4,0,1},{3,4,0.2},{3,4,1,2}
{3,4,0,1,2}