Cubic Formula, Two Ways

Attempting to implement the cubic formula. The first way breaks down when the formula takes the square root of a negative. The second way computes with complex numbers, but I think the cube root might not be working when the square root is real... between a rock and a hard place![br][br]Two examples to try are a=b=c=d=1, and the classic example a=1, b=0, c=-15, d=-4.

Information: Cubic Formula, Two Ways