已知集合A={1,2,3,4,5},B={(x,y)丨x∈A,y∈A,|x-y|∈A},则B中所含元素的个数为( ) A.6 B.12 C.16 D.20
问题描述:
已知集合A={1,2,3,4,5},B={(x,y)丨x∈A,y∈A,|x-y|∈A},则B中所含元素的个数为( )
A. 6
B. 12
C. 16
D. 20
答
∵A={1,2,3,4,5},B={(x,y)|x∈A,y∈A,|x-y|∈A},∴当|x-y|=1时,(1,2),(2,3),(3,4),(4,5),(2,1),(3,2),(4,3),(5,4);当|x-y|=2时,(1,3),(2,4),(3,5),(3,1...