#include<bits/stdc++.h>
using namespace std;
int main(){
	double a,b,c,x1,x2,n;
	cin>>a>>b>>c;
	n=b*b-4*a*c;// 
	if(n>=0)
	{
		x1=(-b+sqrt(n))/(2*a); //第一个根 
		x2=(-b-sqrt(n))/(2*a); //第二个根 
		if(x1==x2) //两根相等 
		{
			cout<<fixed<<setprecision(5)<<"x1=x2="<<x1;
		}
		else if(x1<x2) //第一个小 
		{
			cout<<fixed<<setprecision(5)<<"x1="<<x1<<";x2="<<x2;
		}
		else //第二个小 
		{
			cout<<fixed<<setprecision(5)<<"x1="<<x2<<";x2="<<x1;
		}
	}	
	else //无解 
	{
		cout<<"No answer!";
	}
 return 0;
}

有的兄弟有的

#include<bits/stdc++.h>
using namespace std;
int main()
{
	double a,b,c,x1/*根1*/,x2/*根2*/,n;
	cin>>a>>b>>c;
	n = b*b-4*a*c;
	if (n>=0)//有解
	{
		x1 = (-b+sqrt(n))/(2*a);//根1
		x2 = (-b-sqrt(n))/(2*a);//根2
		if (n==0) cout<<fixed<<setprecision(5)<<"x1=x2="<<x1;//根相等
		else if (x1<x2) cout<<fixed<<setprecision(5)<<"x1="<<x1<<";x2="<<x2;
		else cout<<fixed<<setprecision(5)<<"x1="<<x2<<";x2="<<x1;
	}
	else cout<<"No answer!";//无解
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    double a,b,c,x1,x2;
    cin>>a>>b>>c;
    if ((b*b-4*a*c)<0)
    {
        cout<<"No,answer!";
    }
    else{
        x1 = (-b+sqrt(pow(b,2)-4*a*c))/(2*a);
        x2 = (-b-sqrt(pow(b,2)-4*a*c))/(2*a);
        if ((b*b-4*a*c)==0)
        {
            cout<<"x1=x2="<<fixed<<setprecision(5)<<x1;
        }
        else if((b*b-4*a*c)>0){
            if(x1 < x2)
        {
            cout<<"x1="<<fixed<<setprecision(5)<<(-b+sqrt(pow(b,2)-4*a*c))/(2*a)<<';'<<"x2="<<(-b-sqrt(pow(b,2)-4*a*c))/(2*a);
        }else{
            cout<<"x1="<<fixed<<setprecision(5)<<(-b-sqrt(pow(b,2)-4*a*c))/(2*a)<<';'<<"x2="<<(-b+sqrt(pow(b,2)-4*a*c))/(2*a);
        
        }
        }

    }
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main(){
	double a,b,c,x1,x2,n;
	cin>>a>>b>>c;
	n=b*b-4*a*c;
	if(n>=0)
	{
		x1=(-b+sqrt(n))/(2*a); 
		x2=(-b-sqrt(n))/(2*a);  
		if(x1==x2) 
		{
			cout<<fixed<<setprecision(5)<<"x1=x2="<<x1;
		}
		else if(x1<x2)  
		{
			cout<<fixed<<setprecision(5)<<"x1="<<x1<<";x2="<<x2;
		}
		else  
		{
			cout<<fixed<<setprecision(5)<<"x1="<<x2<<";x2="<<x1;
		}
	}	
	else  
	{
		cout<<"No answer!";
	}
 return 0;
}