discriminant method
The discriminant of the algebraic equation if it exists.
Implementation
@override
Complex discriminant() {
final p1 = c * c * b * b;
final p2 = d * b * b * b * const Complex.fromReal(4);
final p3 = c * c * c * a * const Complex.fromReal(4);
final p4 = a * b * c * d * const Complex.fromReal(18);
final p5 = d * d * a * a * const Complex.fromReal(27);
return p1 - p2 - p3 + p4 - p5;
}