printf("%.4f", f(l));

#include <bits/stdc++.h>
using namespace std;
double N;
double n;
double a[1000000], b[1000000], c[1000000];

double f(double x) {
	double ans = -1;
	for (int i = 0; i < n; i++)
		ans = max(ans, a[i]  * x * x + b[i]  * x + c[i]);
	return ans;
}

int main() {
	cin >> N;
	for (int j = 0; j < N; j++) {
		cin >> n;
		for (int i = 0; i < n; i++) {
			cin >> a[i] >> b[i] >> c[i];
		}

		double l = 0, r = 1000;
		while (fabs(r - l) > 1e-9) {
			double m1 = l + (r - l) / 3;
			double m2 = m1 + (r - l) / 3;
			if (f(m1) > f(m2))
				l = m1;
			else
				r = m2;
		}
		printf("%.4f", f(l));

	}
}