void quadratic_equation(double a4,double b4,double c4,complex<double> &z1,complex<double> &z2)
{
double delta;
complex<double> temp1,temp2;
delta=b4*b4-4*a4*c4;
complex<double> temp(delta,0);
temp1 = (-b4)/(2*a4);
temp2 = sqrt(temp)/(2*a4);
z1=temp1+temp2;
z2=temp1-temp2;
}