If x = -6 and y = -3, what is the value of 4(x-y)^2 - xy ?
Pick one:  A) 20  B) 18  C) 17  D) 22  E) 23

Rationale: x = - 6 and y = - 3 x - y = - 6 - ( - 3 ) = - 6 + 3 = - 3 x * y = - 6 * - 3 = 18 now we apply it in the equation 4 ( x - y ) ^ 2 - xy = 4 ( - 3 ) ^ 2 - 18 = = > 4 * 9 - 18 = 36 - 18 = 18 answer : b
Answer: B