5*(x - 4) - (x + 4)*(x - 4)
-20 + 5*x - (-4 + x)*(4 + x)
-20.0 + 5.0*x - (4.0 + x)*(-4.0 + x)
(1 - x)*(-4 + x)
2 -4 - x + 5*x
-(-1 + x)*(-4 + x)