Complex Number LTNC

#include <iostream> //
#include <string>
#include <math.h>
using namespace std; //
class Complex{
protected:
    double real;
    double img;
public:
    Complex(double real,double img)
    {
        this->real = real;
        this->img = img;
    }
    Complex()
    {
        this->real = 0.0;
        this->img = 0.0;
    }
    Complex operator+(const Complex& rhs)
    {
        Complex result;
        result.real = this->real + rhs.real;
        result.img = this->img + rhs.img;
        return result;
    }
     Complex operator+(double realNum)
    {
        Complex result;
        result.real = this->real + realNum;
        result.img = this->img;
        return result;
    }
    Complex operator-(const Complex& rhs)
    {
        Complex result;
        result.real = this->real - rhs.real;
        result.img = this->img - rhs.img;
        return result;
    }
     Complex operator-(double rhs)
    {
        Complex result;
        result.real = this->real - rhs;
        result.img = this->img;
        return result;
    }
    Complex operator*(const Complex& rhs)
    {
        Complex result;
        result.real = this->real * rhs.real * 1.0 - this->img * rhs.img * 1.0;
        result.img = this->real * rhs.img * 1.0 + this->img * rhs.real * 1.0;
        return result;
    }
    Complex operator * (double rhs)
    {
        Complex result;
        result.real = this->real * rhs * 1.0;
        result.img = this->img * rhs * 1.0;
        return result;
    }
    Complex operator / (const Complex& rhs)
    {
        if (rhs.real == 0 && rhs.img == 0)
        {
            throw ("Error! Divide by zero\n");
        }
        Complex result;
        result.real = this->real * rhs.real * 1.0 - this->img * rhs.img * 1.0;
        result.real = 1.0 * result.real / (rhs.real * rhs.real + rhs.img * rhs.img);
        result.img = this->real * rhs.img * 1.0 + this->img * rhs.real * 1.0;
        result.img = 1.0 * result.img / (rhs.real * rhs.real + rhs.img * rhs.img);
        return result;
    }
    Complex operator / (double rhs)
    {
        Complex result;
        if (rhs == 0)
        {
            throw ("Error! Divide by zero\n");

        }
        result.real = 1.0 * this->real / rhs;
        result.img = 1.0 * this->img / rhs;
        return result;
    }
    friend ostream& operator<<(ostream& os, const Complex& rhs)
    {
        if (rhs.img > 0) os << rhs.real << " +" << rhs.img << "i";
        else os << rhs.real << " -" << -rhs.img << "i";
        return os;
    }
      friend istream& operator>>(istream& in,Complex& rhs)
    {
       cout << "Nhap phan thuc \n";
       in >> rhs.real;
       cout << "Nhap phan ao\n";
       in >> rhs.img;
       return in;
    }
    friend void ptb2(double a, double b, double c);
};

void ptb2(double a = 0, double b = 0, double c = 0)
    {
        if (a == 0)
        {
            if (b == 0)
            {
                if (c != 0) cout << "Phuong trinh vo nghiem\n";
                else cout << "Phuong trinh co mot nghiem x = 0\n";
                return;
            }
            else
            {
                double res = -1.0*c/b;
                cout << "Phuong trinh co mot nghiem la x = " << res << endl;
                return;
            }
        }
        double delta = b*b - 4 * a *c;
        if (delta == 0)
        {
            double res = -1.0*b/(2*a);
               cout << "Phuong trinh co mot nghiem la x = " << res << endl;
                return;
        }
        if (delta > 0)
        {
            double res1 = -b + sqrt(delta);
            res1 = 1.0*res1/(2*a);
            double res2 = -b - sqrt(delta);
            res2 = 1.0*res2/(2/a);
            cout << "Phuong trinh co hai nghiem la x1 = " << res1 << ", x2 = " << res2 << endl;
            return;
        }
        if (delta < 0)
        {
            Complex res1;
            res1.real = -b/(2*a);
            res1.img = sqrt(-delta)/(2*a);
            Complex res2;
            res2.real = res1.real;
            res2.img = -res1.img;
       cout << "Phuong trinh co hai nghiem la x1 = " << res1 << ", x2 = " << res2 << endl;
            // cout << "Phuong trinh co hai nghiem ao la x1 = " << res1.real << " +" << res1.img << "i"
            // << ", x2 = " << res2.real << " +" << res2.img << endl;
            return;
        }
    }
int main ()
{
    ptb2(1,2,2);
}