Perhaps you meant (a^3+14a^2+33a-20) / (a+4), for division by (a+4).
Do you know synthetic division? If so, that'd be a great way to accomplish this division. Assume that (a+4) is a factor of a^3+14a^2+33a-20; then assume that -4 is the corresponding root of a^3+14a^2+33a-20.
Perform synth. div. If there is no remainder, then you'll know that (a+4) is a factor and will also have the quoitient.
-4 / 1 14 33 -20
___ -4_-40 28___________
1 10 -7 8
Here the remainder is not zero; it's 8. However, we now know that the quotient is 1a^2 + 10a - 7 with a remainder of 8.