The correct option is D (a−b+2c)(a−b−2c)(a+b+2c)(a+b−2c)
(a2+b2−4c2)2−4a2b2
=(a2+b2−4c2)2−(2ab)2
=[a2+b2−4c2+2ab][a2+b2−4c2−2ab]
Using,
(a+b)2=a2+2ab+b2 and (a−b)2=a2−2ab+b2
=[(a+b)2−4c2][(a−b)2−4c2]
Using,
a2−b2=(a+b)(a−b)
=(a+b+2c)(a+b−2c)(a−b−2c)(a−b+2c)