#include<bits/stdc++.h>
using namespace std;
int n;
int a[10001],b[10001],c[10001];
double f(int cnt,double x){	return a[cnt]*x*x+b[cnt]*x+c[cnt];}
double ff(double x){
	double ans=f(1,x);
	for(int i=2;i<=n;i++)	ans=max(f(i,x),ans);
	return ans;
}
double g(){
	double l=0,r=1000;
	while(r-l>1e-10){
		double mid1=l+(r-l)/3.0;
		double mid2=r-(r-l)/3.0;
		if(ff(mid1)>ff(mid2))	l=mid1;
		else	r=mid2;
	}
	return ff(l);
}
int main(){
	int T;
	scanf("%d",&T);
	while(T--){		
		scanf("%d",&n);
		double ans;
		for(int i=1;i<=n;i++)	scanf("%lf %lf %lf",&a[i],&b[i],&c[i]);
		ans=g();
		printf("%.4lf\n",ans);
	}	
	return 0;
}