1. The problem statement, all variables and given/known data Actually, part of a question on modeling/control systems. I need to find the poles (or, roots) of the cubic function. 2. Relevant equations x^3 - 13x + 12 = 0 3. The attempt at a solution The rule of thumb for the course is that if you get a cubic function then there will always be a solution of x equal to -1,0 or 1. For this particular equation, I figured out that it's 1. Now I need 2 more solutions. On my first try I got +/- sqrt(13) by factoring the equation as follows: x(x^2-13x)+12=0 Those are wrong, I checked them. So yeah, question is if someone can help me or point me in the direction of a simple way to solve cubic functions, I have almost no experience with them (normally I'd use my calculator, not allowed for this class). The answers in the appendix say that the other two roots are 3 and -4, if that helps. Thanks in advance!