(y + 2)(y - 4i)(y + 4i)
note that the polynomial = 0 when y = - 2
(-2)³ + 2(- 2)² + 16(- 2) + 32 = - 8 + 8 - 32 + 32 = 0
hence y = - 2 is a root thus (y + 2) is a factor
dividing the polynomial by (y + 2) gives
y³ + 2y² + 16y + 32 = (y + 2)(y² + 16) = (y + 2)(y - 4i)(y + 4i)