hdu 3714

#include <cstdio>  
#include <algorithm>
#include <iostream>
using namespace std;  
  
const int maxn = 10000 + 10;  
int n, a[maxn], b[maxn], c[maxn];  
  
double F(double x)  
{  
    double ans = a[0]*x*x + b[0]*x + c[0];  
    for(int i=1; i<n; ++i)  
        ans = max(ans, a[i]*x*x + b[i]*x +c[i]);  
    return ans;  
}  
  
int main()  
{  
	#ifdef test   
    freopen("c://test.txt","r",stdin);   
	#endif   
    int T;  
    scanf("%d", &T);  
    while(T--)  
    {  
        scanf("%d", &n);  
        for(int i=0; i < n; ++i) scanf("%d%d%d", &a[i], &b[i], &c[i]);  
        double L = 0.0, R = 1000.0;  
        for(i = 0; i < 100; ++i)  
        {  
            double m1 = L + (R - L)/3;  
            double m2 = R - (R - L)/3;  
            if(F(m1) < F(m2) ) R = m2;  
            else L = m1;  
        }  
        printf("%.4lf\n", F(L));  
    }  
    return 0;  
}