How do you solve third order recurrence relations?

[swtlilsoni]

I know how to solve second order ones, but how would you solve third order ones? Because the characteristic polynomial would have a third degree so how can one find the roots?
I have looked everywhere online to find out but I can't find anything. Please Please tell me!

 

[HallsofIvy]

What is the problem with third degree equations? More complicated than quadratic, yes, but still doable. At worst, use Cardano's method:
http://en.wikipedia.org/wiki/Cubic_function.