If x + y = 9 and x – y = 3, then x^2 - y^2 =	Pick one:
A) - 4
B) 4
C) 10
D) 27
E) 40

Rationale: the fastest approach has already been shown . here ' s one more option . given : x + y = 9 x – y = 3 add the two equations to get : 2 x = 12 , which means x = 6 if x = 6 , we can plug that value into either equation , to conclude that y = 3 if x = 6 and y = 3 , then x ² - y ² = 6 ² - 3 ² = 27 answer : d
Answer: D