#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,t;
int a[100000],b[100000],c[100000];
double check(double x,int i){
	double s=a[i]*x*x+b[i]*x+c[i];
	return s;
}
double my(double x){
	double s=0;
	for(int i=1;i<=n;i++)s=max(s,check(x,i));
	return s;
}
signed main(){
	cin>>t;
	while(t--)
	{
		cin>>n;
		for(int i=1;i<=n;i++)cin>>a[i]>>b[i]>>c[i];
		double l=0,r=1000,k=1e-15,ans;
		while(r-l>k){
			double m1=l+(r-l)/3.000,m2=(l-r)/3.000+r;
			if(my(m1)>my(m2))l=m1;
			else r=m2;
		}
		printf("%.4lf\n",my(r));
		for(int i=1;i<=n;i++)a[i]=b[i]=c[i]=0;
	}
	
	return 0;
}