Numbers - General Aptitude

Q1:

(489 + 375)2 - (489 - 375)2 = ?
(489 x 375)

A 144

B 864

C 2

D 4

E None of these

ANS:D - 4

Given Exp. = (a + b)2 - (a - b)2 = 4ab = 4
ab ab