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/sci/ - Science & Math


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>> No.9274542 [View]
File: 101 KB, 1122x584, Screenshot from 2017-11-03 23.53.49.png [View same] [iqdb] [saucenao] [google]

What is this book trying to say here?

>The sets A and B have the same cardinality if and only if there is a one-to-one correspondence
from A to B. When A and B have the same cardinality, we write |A| = |B|.
This is not true, and they even say it is not true in the next definition. It needs to be a bijection and not just one-to-one, right? What point are they trying to make and why are they using a definition which is not true? Am I completely misunderstanding what is being said here?

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