#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
int T,n;
double l,r,mid1,mid2;
double a[10001],b[10001],c[10001];
double f(double aa,double bb,double cc,double x){
    return x*x*aa+x*bb+cc;
}
double F(double x){
    double bns=-0x3f3f3f3f;
    for(int i=1;i<=n;i++)
        bns=max(bns,f(a[i],b[i],c[i],x));
    return bns;
}
int main(){
    cin>>T; 
    while(T--){
        cin>>n;
        for(int i=1;i<=n;i++)
            cin>>a[i]>>b[i]>>c[i];
        l=0.00;r=1000.00;
        while(r-l>=0.0000000001){
            mid1=(2.0*l+r)/3.0;
            mid2=(l+2.0*r)/3.0;
            if(F(mid1)>F(mid2))l=mid1;
            else  r=mid2;
        }
        printf("%.4lf\n",F(l));
    }
}