# Math Help - Proving a function is one-to-one/onto

1. ## Proving a function is one-to-one/onto

I have a function:

$f(m,n) = mn$

The domain for this is $Z \times Z$. The range is $Z$. How can I prove if it is one-to-one, onto, or both?

2. Originally Posted by Projectt
I have a function:
$f(m,n) = mn$
The domain for this is $Z \times Z$. The range is $Z$. How can I prove if it is one-to-one, onto, or both?
It is clearly not one-to-one: $f(2,3)=f(3,2)$.
Is it onto? If $z\in \mathbb{Z}$ then is it possible that $f(?,?)=z$?

3. Ohh, I thought Z was some arbitrary set, not the set of all integers. Thanks.