What is 16x4 - 100y4 factored completely?
(4x2 + 10y2)(2x - 5y)(2x + 5y)
(2x - 5y)2 (2x + 5y)
16(x2 - 5y2)(x2 + 5y2)
4(2x2 - 5y2)(2x2 + 5y2)