English: The w:Discriminant of the quartic polynomial x^4+a x^2+b x + c. The surface represents point (a,b,c) where the polynomial has a repeated root, the cuspidal edge correspond to polynomials with a triple root and the self intersection to the polynomials with two different repeated roots. This surface satisfies the equation -4 a^3 b^2 - 27 b^4 + 16 a^4 c -128 a^2 c^2 + 144 a b^2 c + 256 c^3 - 0. It was generated from the Singsurf program.