题目内容
函数其中P,M为实数集R的两个非空子集,又规定f(P)={y|y=f(x),x∈P},f(M)={y|y=f(x),x∈M}.给出下列四个判断:
①若P∩M=,则f(P)∩f(M)=
;②若P∩M≠
,则f(P)∩f(M)≠φ;
③若P∪M=R,则f(P)∪f(M)=R;④若P∪M≠R,则f(P)∪f(M)≠R.
其中正确判断有
[ ]
A.0个
B.1个
C.2个
D.4个
答案:A
解析:
解析:
若P={1},M={-1}则f(P)={1},f(M)={1}则f(P)∩f(M)≠ 若P={1,2},M={1}则f(P)={1,2},f(M)={1}则f(P)∩f(M)= 若P={非负实数},M={负实数}则f(P)={非负实数},f(M)={正实数}则f(P)∪f(M)≠R. 故③错.若P={非负实数},M={正实数}则f(P)={非负实数},f(M)={负实数}则f(P)∪f(M)=R.故④错 |
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①若
P∩M=
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②若
P∩M
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③若
P∪M=R,则f(P)∪f(M)=R;④若
P∪M
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其中正确判断有
[
]
A .1个 |
B .2个 |
C .3个 |
D .4个 |
(2004
北京,8)函数
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[
]
A .1个 |
B .2个 |
C .3个 |
D .4个 |