How do you factor 4x squared - 16?

(2x + 4)(2x - 4)

to check your answer, use the FOIL method

(first, outside, inside, last)

F.... 2x x 2x = 4x^2

0.... 2x x -4 = -8x

I..... 2x x 4 = 8x

L.... 4 x -4 = -16

so 4x^2 - 16 = (2x + 4)(2x - 4)