#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include<cassert>
#include<set>
using namespace std ;
#ifdef DeBUG
#define bug assert
#else
#define bug //
#endif
#define eps 1e-10
double a[10010],b[10010],c[10010];
int m;
inline double f(double x)
{
int i;
double maxx=a[0]*x*x+b[0]*x+c[0];
for(i=1;i<m;i++)
maxx=max(maxx,a[i]*x*x+b[i]*x+c[i]);
return maxx;
}
int main()
{
#ifdef DeBUG
freopen("C:\Users\Sky\Desktop\1.in","r",stdin);
#endif
int n;
scanf("%d",&n);
int i,j,k;
while(n--)
{
scanf("%d",&m);
for(i=0;i<m;i++)
scanf("%lf%lf%lf",&a[i],&b[i],&c[i]);
double left=0.0,right=1000.0,mid,midmid;
while(right-left>eps)
{
mid=(right+left)/2;
midmid=(mid+right)/2;
if(f(mid)>f(midmid))
{
left=mid;
}
else
{
right=midmid;
}
}
printf("%.4lf
",f(mid));
}
return 0;
}