Evaluate this $\sqrt[3]{\frac{-q}{2} + \sqrt{(\frac{q}{2})^2 + (\frac{p}{3})^3}} + \sqrt[3]{\frac{-q}{2} - \sqrt{(\frac{q}{2})^2 + (\frac{p}{3})^3}}$ using the cubic formula which applies to $q=d \ and \ p=c$ x^3 + x^2 + x + 1=0
So, you just want to solve x^3 + x^2 + x + 1 = 0?