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(Solve Any 3rd Degree Polynomial Equation) I'm putting this on the web because some students might find it interesting. It could easily be mentioned in many undergraduate math courses, though it doesn't seem to appear in most textbooks used for those courses. None of this material was discovered by me. -- ES You should know that the solution of ax2+bx+c=0 is There is an analogous formula for polynomials of degree three: The solution of ax3+bx2+cx+d=0 is (A formula like this was first published by Cardano in 1545.) Or, more briefly, x   =   {q + [q2 + (r-p2)3]1/2}1/3   +   {q - [q2 + (r-p2)3]1/2}1/3   +   p where p = -b/(3a),    q = p3 + (bc-3ad)/(6a2),    r = c/(3a) But I do not recommend that you memorize these formulas. Aside from the fact that it's too complicated, there are other reasons why we don't teach this formula to calculus students. One reason is that we're trying to avo...