题目链接
注意特殊情况
当a等于0和b等于0时，因为都有可能放在分母！

#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a,b,c;
	while(cin>>n){
		while(n--){
			cin>>a>>b>>c;
			
			int delta = b*b-4*a*c;
			if(a==0&&b!=0) printf("x=%.2f\n",-c*1.0/b); 
			else if(delta>0){
				double x1 = (-b-sqrt(delta))/2.0/a;
				double x2 = (-b+sqrt(delta))/2.0/a;
				printf("x1=%.2f,x2=%.2f\n",x1,x2);
			}else if(delta==0){
				double x = (-b)/2.0/a;
				printf("x=%.2f\n",x);
			}else cout<<"-1\n";
		}
	} 
	return 0;
}