Determine whether f Z x Z Z is onto I have no idea how to d

Determine whether f: Z x Z --> Z is onto. I have no idea how to do this with two variables

a) f(m,n) = m+n

b) f(m,n) = m^2 + n^2

Solution

F(m,n)= m+n will be onto function only incase (0,0) and (1,1), other cases its not onto function

f(m,n) = m^2 + n^2 will be onto function only for (0,0) and (2,2),other cases its not onto function

As set Z is not defined we can only say for what values it will onto