#include<cstdio>

#include<cstring>

#include<iostream>

#include<algorithm>

#define MAXN 10100

#define eps 1e-9

using namespace std;

int T,n;

double ans;

double l,r,mid1,mid2;

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

double f(double x){

    ans=-0x7f7f7f7f;

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

    return ans;

}

int main(){

    scanf("%d",&T);

    while(T--){

        scanf("%d",&n);

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

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

        l=;r=;

        while(r-l>eps){

            mid1=(l+r)/;

            mid2=(mid1+r)/;

            if(f(mid1)>f(mid2))    l=mid1;

            else r=mid2;

        }

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

    }

}