Hi,(adsbygoogle = window.adsbygoogle || []).push({});

Say f:A->A where A is a metric space and f is onto. I think it should be true that this implies that f is also one to one. Is there a way to formally prove this?

Thanks.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# F maps A onto A=>f is one to one

**Physics Forums | Science Articles, Homework Help, Discussion**