求解 为什么运行结果不对啊？？

非常精彩，欣赏支持好友佳作

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
    double a,b,c;
    double delta,x1,x2;
    int sign,stop;
    cout<<"请输入3个系数a(a!=0),b,c"<<endl;
    cin>>a>>b>>c;
    delta=b*b-4*a*c;
    if(a==0)
    {
        cout<<"a不能等于0，不是一元二次方程"<<endl;
    }
    else
    {
        if(delta==0)
        {
            cout<<"方程有两个实根:x1=x2="<<-b/(2*a)<<endl;
        }
        else
        {
            if(delta>0)
                sign=1;
            else
                sign=0;
            delta=sqrt(fabs(delta));
            x1=-b/(2*a);
            x2=delta/(2*a);
            if(sign){
                cout<<"方程有两个不同的实根：x1="<<x1+x2<<"  "<<"x2="<<x1-x2<<endl;
            }
            else{
                cout<<"方程无实根，有两个不同的复数根：x1="<<x1<<"+i"<<"  "<<x2<<"x2="<<x1<<"-i"<<x2<<endl;
            }
        }
    }
}