The Cartesian product A × A has 9 elements among which are found (–1, 0) and (0,1). Find the set A and the remaining elements of A × A.
(2x, x+y) = (6, 2)
2x = 6 or x =3
and x+y = 2 or 3+y = 2 or y = -1
Hence, x = 3, y = -1
Let A = {1, 2}, B = {1, 2, 3, 4}, C={5, 6} and D = {5, 6, 7, 8}. Verify that A x C is a proper subset of B x D.