ans

#include<iostream>
using namespace std;
int n;
struct func {
	int a, b, c;
}f[10001];
double value(double x) {
	double ans = -1e18;
	for (int i = 1; i <= n; i++) {
		ans = max(f[i].a * x * x + f[i].b * x + f[i].c, ans);
	}
	return ans;
}
int main() {
	int t;
	cin >> t;
	for (int a = 0; a < t; a++) {
		cin >> n;
		for (int i = 1; i <= n; i++) cin >> f[i].a >> f[i].b >> f[i].c;
		double left = 0, right = 1000;
		while (right - left > 1e-9) {
			double lmid = (right - left) / 3 + left;
			double rmid = right - (right - left) / 3;
			if (value(lmid) > value(rmid)) {
				left = lmid;
			}
			else {
				right = rmid;
			}
		}
		printf("%.4lf\n", value(left));
	}
	return 0;
}