Others are equal to 3x2 + 8xy + 4y2
Four of the five parts numbered (a), (b), (c), (d) and (e) in the following equation are exactly equal. Which part is not equal to the other four ? The number of that part is the answer.
(a) (x + 2y) (3x + 2y) 
(b) (x + 2y) 2 + 2x(x + 2y) 
(c) (3x + 2y) 2 – 2x(3x + 2y) 
(d) 3x(x + 2y)  + 2y(x + 2y) 
(e) x(3x + 2y)  – 2y(3x – 2y) 