题目内容
【题目】已知集合A={1,2,3,4,5},B={(x,y)|x∈A,y∈A,x-y∈A},则B中所含元素的个数为 _______.
【答案】10
【解析】∵x∈A,y∈A,x-y∈A,
∴满足条件的(x,y)有(2,1),(3,2),(4,3),(5,4),(3,1),(4,2),(5,3),(4,1),(5,2),(5,1),共10个.
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