Domain of a set of ordered pairs
We know the domain is the set of all x when is represented by ordered pairs: (x, y)
In this case {(-8,-12),(4,-8), (2, -10),(-10.-16) } we can observe that there are four x (the first number of each pair):
Domain = { -8, 4, 2, -10}
Domain = {-10, -8, 2, 4}