Determine whether the given function is one to one and whether it is onto. If the function is both one to one and onto, find the inverse of the function.

f:R^2---->R^2, f(x,y)=(x+y, y) .

I know one to one says f(x)=f(y) implies x=y

Onto means if for every element y in R^2 , there exists an element x in R^2 with f(x)=y.

I conceptually understand the idea, but don't know how to use these definitions.