#include<iostream>
#include<math.h>
using namespace std;
class Complex
{
private:
    double real,imag;
public:
    Complex (double,double);
    void set (double,double);
    void printf();

};

void Complex::set (double r,double i)
{
    real=r;
    imag=i;
}

void Complex::printf()
{
    cout<<real<<"+"<<imag<<"i"<<endl;
    cout<<real<<"-"<<imag<<"i"<<endl;
}

class Equation
{
private:
    double a,b,c,delta;
    Complex root1,root2;
    
public:
  Equation(double a1,double b1,double c1)
    {
        a=a1;b=b1;c=c1;
    }
    
    bool isEquation()
    {
    return(a!=0);
        
    }
    
    void countDelta()
    {
        delta=b*b-4*a*c;
    }
    
    Complex getFirstRoot()
    {
        root1=(-b+sqrt(delta))/2*a;
    }
    
    Complex getSecondRoot()
    {
        root2=(-b-sqrt(delta))/2*a;
    }
    
    void resolve()
    { double r1,r2,i1,i2;
        if(delta<0)
        {
        r1=(-b)/2*a;
        i1=sqrt(-delta)/2*a;
        r2=r1;
        i2=i1;
        }
        else if(delta=0)
        
              {
        
            r1=(-b+sqrt(delta))/2*a;
            i1=0;
            r2=r1;
            i2=0;
        }    
             else   
             {
             r1=(-b+sqrt(delta))/2*a;
             i1=0;
             r2=(-b-sqrt(delta))/2*a;
             i2=0;
             }

        
        
    
    }
};
    
    void main()
    {
        double a,b,c;
        cout<<"输入方程系数："<<endl;
        cin>>a>>b>>c;
        Equation equation=new Equation(a,b,c);
        if(equation.isEquation())
        { 
            equation.countDelta();
            equation.resolve();
            Complex r1=equation.getFirstRoot();
        Complex r2=equation.getSecondRoot();
            r1.printf();
            r2.printf();
        }
        else
        {
        cout<<"该方程不是二元一次方程"<<endl;
        }
    }

但是有错误：
error C2512: 'Complex' : no appropriate default constructor available