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2012届高考数学临考适应性训练:选择题(40)1.已知集合P={x|x2=1},Q={x|mx=1},若Q?P,则实数m的数值为 ( )A.1 B.-1 C.1或-1 D.0,1或-1答案:D解析:当m=0时,Q=??P;当m≠0时,由Q?P知,x=1m=1或x=1m=-1,得m=1或m=-1.2.已知U={2,3,4,5,6,7},M={3,4,5,7},N={2,4,5,6},则 ( )A.M∩N={4,6} B.M∪N=UC.(?UN)∪M=U D.(?UM)∩N=N答案:B解析:由题意得M∩N={4,5},M∪N={2,3,4,5,6,7}=U,(?UN)∪M={3,4,5,7}≠U,(?UM)∩N={2,6}≠N,综上所述,选B.3.已知空集U=A∪B中有m个元素,(?UA)∪(?UB)中有n个元素.若A∩B非空,则A∩B的元素个数为 ( )A.mn B.m+n C.n-m D.m-n答案:D解析:依题意,结合韦恩图分析可知,集合A∩B的元素个数是m-n,选D.4.设集合A={x|-12<x<2},B={x|x2≤1},则A∪B= ( )