Question

离散数学中有四个元素的集合能确定多少种相容关系

Answer 1

设A={1,2,3,4},A上有8个相容（自反,对称）关系：

{(1,1),(2,2),(3,3),(4,4)};

{(1,1),(2,2),(3,3),(4,4),(1,2),(2,1)};

{(1,1),(2,2),(3,3),(4,4),(1,3),(3,1)};

{(1,1),(2,2),(3,3),(4,4),(2,3),(3,2)};

{(1,1),(2,2),(3,3),(4,4),(1,2),(2,1),(1,3),(3,1)};

{(1,1),(2,2),(3,3),(4,4),(2,3),(3,2),(1,3),(3,1)};

{(1,1),(2,2),(3,3),(4,4),(1,2),(2,1),(2,3),(3,2)};

{(1,1),(2,2),(3,3),(4,4),(1,2),(2,1),(2,3),(3,2),(1,3),(3,1)};