#include <bits/stdc++.h>
using namespace std;

const int N = 1000010;
const double eps=1e-6;
double a[N],b[N],c[N];
int t;
int n;

double get(double mid)
{
	double mi=-11451411;
	for(int i=1;i<=n;i++) mi=max(mi,a[i]*mid*mid+b[i]*mid+c[i]);
	return mi;
}
int main()
{
	scanf("%d",&t);
	while(t--)
	{
		scanf("%d",&n);
		for(int i=1;i<=n;i++) scanf("%lf%lf%lf",&a[i],&b[i],&c[i]);
		double l=0.0000,r=1000.0000,best=-1;
		while(r-l>eps)
		{
			double mid1=l+(r-l)/3.00;
			double mid2=r-(r-l)/3.00;
			if(get(mid1)<get(mid2)) best=mid1,r=mid2;
			else best=mid2,l=mid1;
		}
		printf("%.4lf\n",best);
	}
}