#include <cstdio>

 #include <algorithm>

 using namespace std;

 const int maxn =  + ;

 int n;

 double a[maxn], b[maxn], c[maxn];

 double F(double x)

 {

     double ans = a[]*x*x+b[]*x+c[];

     for(int i = ; i < n; i++)

         ans = max(ans, a[i]*x*x+b[i]*x+c[i]);

     return ans;

 }

 int main()

 {

     //freopen("in.txt", "r", stdin);

     int T;

     scanf("%d", &T);

     while(T--)

     {

         scanf("%d", &n);

         for(int i = ; i < n; i++) scanf("%lf%lf%lf", &a[i], &b[i], &c[i]);

         double L = 0.0, R = 1000.0;

         for(int i = ; i < ; i++)

         {

             double m1 = L + (R-L)/;

             double m2 = R - (R-L)/;

             if(F(m1) < F(m2)) R = m2;

             else L = m1;

         }

         printf("%.4f\n", F(L));

     }

     return ;

 }