C++ :

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
#define MAXN 10010
#define inf 0x7fffffff
int t,n;
int a[MAXN],b[MAXN],c[MAXN];
inline int read(){
	int x=0,t=1,c;
	while(!isdigit(c=getchar())) if(c=='-') t=-1;
	while(isdigit(c)) x=x*10+c-'0',c=getchar();
	return x*t;
}
double calc(double x){
	double maxn=-inf;
	for(int i=1;i<=n;i++) maxn=max(maxn,a[i]*x*x+b[i]*x+c[i]);
	return maxn;
}
void sanfen(){
	double l=0,r=1000;
	while(l+1e-10<r){
		double lmid=l+(r-l)/3.0,rmid=r-(r-l)/3.0;
		if(calc(lmid)<=calc(rmid)) r=rmid;
		else l=lmid;
	}
	printf("%.4lf\n",calc(l));
}
int main(){
	t=read();
	while(t--){
		n=read();
		for(int i=1;i<=n;i++) a[i]=read(),b[i]=read(),c[i]=read();
		sanfen();
	}
	return 0;
}