#include <bits/stdc++.h>
using namespace std;
int t,n;
struct two_pow_function
{
	int a,b,c;
}f[1005];
double f_val(double x,int i)
{
	return x*x*f[i].a+x*f[i].b+f[i].c;
}
double f_max(double x)
{
	double fx_max=f_val(x,1);
	for (int i=2;i<=n;i++)
	{
		fx_max=max(f_val(x,i),fx_max);
	}
	return fx_max;
}
int main()
{
	cin>>t;
	while(t--)
	{
		cin>>n;
		for (int i=1;i<=n;i++)
		{
			cin>>f[i].a>>f[i].b>>f[i].c;
		}
		double l=0,r=1000,tl,tr;
		while (r-l>1e-11)
		{
			tl=l+(r-l)/3.0;
			tr=r-(r-l)/3.0;
			if (f_max(tl)>f_max(tr))
			{
				l=tl;
			}
			else
			{
				r=tr;
			}
			
		}
		printf("%.4lf\n",l);
	}
	return 0;
}