We all know the solution of ax2+bx+c=0. There is an analogous formula for polynomials of degree three. See https://math.vanderbilt.edu/schectex/courses/cubic/
Thank you Prof. Ada, I already know the method of Cardano for solveing the equation of the third degree. I am asking about a new treatment to solve the third degree equation by using the method used to solve the fourth degree equation
If we multiply a cubic equation x3+ax2+bx +c = 0 with (x-α), where α is a (suitable) real number, then we obtain the algebraic equation of degree 4, whose solutions can be obtained using routine calculations applying Ferrari’s method. Namely, one of these four solution is α, while other three solutions are in fact the solutions of given equation x3+ax2+bx +c = 0.