#include <bits/stdc++.h>
using namespace std;
using LL=long long;
const double eps=1e-9;
LL n,a[100006],b[100006],c[100006],t;
double solve (double mid) {
	double ans=-1e9;
	for (LL i=1;i<=n;++i) {
		ans=max(ans,1.0*a[i]*mid*mid+b[i]*mid+c[i]);
	}
	return ans;
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>t;
	while (t--) {
		cin>>n;
		for (LL i=1;i<=n;++i) {
			cin>>a[i]>>b[i]>>c[i];
		}
		double l=0,r=1000;
		while (r-l>=eps) {
			double mid1=l+(r-l)/3,mid2=r-(r-l)/3;
			if (solve(mid1)<=solve(mid2)) {
				r=mid2;
			}else {
				l=mid1;
			}
		}
		printf("%.4lf\n",solve(l));
	}
	return 0;
}