The simplified form of $(x + 2y)^3 + (x - 2y)^3 $ is :
Answer & explanation
Correct answer: option 1
(x + 2y)3 + (x - 2y)3
a3 + b3 = (a + b)(a2 + b2 - ab)
(x + 2y)3 + (x - 2y)3 = (x + 2y + x - 2y)[(x + 2y)2 + (x - 2y)2 - (x + 2y)(x - 2y)]
= (x + x)[(x2 + 4y2 + 4xy + x2 + 4y2 - 4xy - x2 + 4y2)]
= 2x(x2 + 12y2)
= 2x3 + 24 xy2