Question

 What is the domain and range of the function f that assigns to each pair of negative integers x and y, the value x + y.

Answer 1

Let $\Z^{-}$  is the set of all negative integers $(..., -3, -2, -1).$ Then

Domain: $\Z^-\times\Z^-$

Range: $\Z^{-}\backslash \{-1\}$