How To Find The Real Roots Of A Cubic Polynomial. Now let us consider the following polynomial for a cubic equation: The nature of roots of all cubic equations is either one real root and two imaginary roots or three real roots.

The cubic formula given above calculates the real root. If the discriminant is zero, we have a single root. Consider the cubic polynomial p(t)=t3 − 2t2 − 5t + 6.