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单射满射双射的区别

更新时间: 2020-07-13 00:00:00     

单射:对于集合A中的每一个元素a,B中都有唯一的元素b和它对应,这样的映射叫单射。a叫b的原像;

满射:对于单射f,如果B中的每一个元素都有原像,那么f叫满射;

双射:对于满射f,如果B中的每一个元素都有唯一的原像,那么f叫双射。

关键词: 区别

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