> Unless my eyes deceive me, this is equivilent:
> 
> J = 2a^3 - 9ab + 26c
> K = Sqrt(J^2 + 4(-a^2 + 3b)^3)
> M = (1 + i Sqrt(3))/2
> N = (-1 + i Sqrt(3))/2
> 
> r1 = -(a/3) +   Cbrt((-J + K)/54) +   Cbrt((-J - K)/54)
> r2 = -(a/3) + M Cbrt((-J + K)/54) + N Cbrt((-J - K)/54)
> r3 = -(a/3) + N Cbrt((-J + K)/54) + M Cbrt((-J - K)/54)
> 
> While hardly on the same level as the quadratic, it's not "that" hard.

Did you try to derive those equations from ax^3+bx^2+cx+d=0 ?? :-)

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