Question

设f:x→y=2^x是A→B的映射,已知集合B={0,1,2,3,4},则A满足(   )

A.A={1,2,4,8,16}

B.A={0,1,2,log23}

C.A{0,1,2,log23}

D.不存在满足条件的集合

Answer 1

C

解析:A中每个元素在集合中都有象,令2^x=0,方程无解.分别令2^x=1,2,3,4,解得x=0,1,

log₂3,2.