#pragma GCC optimize(3,"Ofast","inline")

 #include<iostream>

 #include<cstdio>

 #define N 100005

 #define eps 1e-9

 using namespace std;

 int read()

 {

     int x=,f=;char ch=getchar();

     while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}

     while(ch>=''&&ch<=''){x=x*+ch-;ch=getchar();}

     return x*f;

 }

 int t,n;

 double ans,a[N],b[N],c[N];

 double check(double x)

 {

     double r=-;

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

     {

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

     }

     return r;

 }

 signed main()

 {

     //freopen("1.in","r",stdin);

     t=read();

     while(t--)

     {

         n=read();

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

         {

             a[i]=read();

             b[i]=read();

             c[i]=read();

         }

         double l=,r=,lmid,rmid;

         while(l+eps<r)

         {

             rmid=r-(r-l)/3.0;

             lmid=l+(r-l)/3.0;

             if(check(lmid)<=check(rmid))r=rmid;

             else l=lmid;

         }

         printf("%.4lf\n",check(l));

     }

     return ;

 }