A123Bxyx的知识精选

已知*A={1,2,3},B={(x,y)|x∈A,y∈A,x+y∈A},则*B的子集的个数为(  )(A...
问题详情:已知*A={1,2,3},B={(x,y)|x∈A,y∈A,x+y∈A},则*B的子集的个数为()(A)4   (B)7   (C)8   (D)16 【回答】C解析:因为*A={1,2,3},B={(x,y)|x∈A,y∈A,x+y∈A},所以*B={(1,1),(1,2),(2,1)},*B的子集的...
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