//假定b2-4ac>=0,a!=0
#include<iostream>
#include<math.h> //for sqrt
using namespace std;
int main()
{
double a,b,c;
cout<<"Enter a:";
cin>>a;
cout<<"Enter b:";
cin>>b;
cout<<"Enter c:";
cin>>c;
cout<<"x1 = "<<(-b+sqrt(b*b-4*a*c))/(2*a)<<endl;
cout<<"x1 = "<<(-b-sqrt(b*b-4*a*c))/(2*a);
}