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.