How to prove injection and surjection for a function with 2 variables?

[pmooney12]

how do you prove injection and surjection of the function of 2 variables. for example f:RxR->R

 

[micromass]

The same way you prove it for 1 variable.
Can you give us a specific map?

 

[micromass]

For example the map f:RxR--> R:x-->x+y.

This is not an injection, since f(1,0)=f(0,1).
This is a surjection. Take a in R, then f(a,0)=a.