This trick which transforms the general cubic equation into a new cubic equation with missing x2 -term is due to Nicolo Fontana Tartaglia 1500-1557. Uses the cubic formula to solve a third-order polynomial equation for real and complex solutions. The general strategy for solving a cubic equation is to reduce it to a quadratic equation and then solve the quadratic by the usual means either by factorising or using the formula.
Ax3 bx2 cx1d 0 ax3 bx2 cx1 d 0.
Set one side of equation equal to 0. Then one solves the depressed cubic. How to Solve a Cubic Equation Method 1of 3. A x 3 b x 2 c x 1 d 0.