/*

     三分：凹(凸)函数求极值

 */

 #include <cstdio>

 #include <algorithm>

 #include <cstring>

 #include <cmath>

 using namespace std;

 const int MAXN = 1e4 + ;

 const int INF = 0x3f3f3f3f;

 const double EPS = 0.0000000001;

 struct F    {

     double a, b, c;

 }f[MAXN];

 int n;

 double cal(double x)    {

     double res = -INF;

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

         res = max (res, f[i].a * x * x + f[i].b * x + f[i].c);

     }

     return res;

 }

 int main(void)  {       //HDOJ 3714 Error Curves

     //freopen ("HDOJ_3714.in", "r", stdin);

     int T;  scanf ("%d", &T);

     while (T--) {

         scanf ("%d", &n);

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

             scanf ("%lf%lf%lf", &f[i].a, &f[i].b, &f[i].c);

         }

         double l = 0.0, r = 1000.0;

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

             double mid = (l + r) / ;

             double rmid = (mid + r) / ;

             if (cal (mid) < cal (rmid)) r = rmid;

             else    l = mid;

         }

         printf ("%.4f\n", cal (r));

     }

     return ;

 }