Multiply:  x2 + 4x + 16 x - 4

Strategy:
Multiply EVERY term above by EACH term below
Arrange these products in columns by degree.
Add the coefficients in each column.
Some sums may be ZERO.

Multiply:  x2 + 4x + 16 x - 4 -4x2 - 16x - 64 x3 + 4x2 + 16x      x3                 - 64

Answer is: x3 - 64