What's wrong with this function to solve cubic equations?

Question

I am using Python 2 and the fairly simple method given in Wikipedia\'s article \"Cubic function\". This could also be a problem with the cube root function I have to define

Answer 1

Hooked's answer is the way to go if you want to do this numerically. You can also do it symbolically using sympy:

>>> from sympy import roots
>>> roots('2*x**3 + 8*x**2 - 8*x - 32')
{2: 1, -4: 1, -2: 1} 

This gives you the roots and their multiplicity.