To multiply this out..
4(x + 4)(x - 1)
First we can multiply the 4 by (x + 4)
= (4x + 16)(x - 1)
Next, let's multiply the (4x + 16) by (x - 1) ...to do this, we need to multiply each thing in the first set of parenthesees by each thing in the second set of parenthesees and add the products together.
= (4x)(x) + (4x)(-1) + (16)(x) + (16)(-1)
= 4x2 - 4x + 16x - 16
= 4x2 + 12x - 16