determinant method

Implementation

double determinant() {
  final double x =
      _m3storage[0] * ((_m3storage[4] * _m3storage[8]) - (_m3storage[5] * _m3storage[7]));
  final double y =
      _m3storage[1] * ((_m3storage[3] * _m3storage[8]) - (_m3storage[5] * _m3storage[6]));
  final double z =
      _m3storage[2] * ((_m3storage[3] * _m3storage[7]) - (_m3storage[4] * _m3storage[6]));
  return x - y + z;
}