(4) 2[-x - y]^2 + 3(y - x)
(a) x = 0, y = -3
(b) x = -1, y = -2
(c) x = 4, y = -1
(5) (3x + y) / 4xy
(a) x = 0, y = -3
(b) x = -1, y = -2
(c) x = 4, y = -1
(6) a^3 - 3a^2b + 3ab^2 - b^3
(a) a = 2, b = 3
(b) a = 0, b = -2
(c) a = -1, b = -3
(7) (a - b)^3
(a) a = 2, b = 3