求助 subtask 2

#include<bits/stdc++.h>
using namespace std;
int t,i,n;
double a[10009],b[10009],c[10009];
double calc(int i,double x)
{
	return a[i]*x*x+b[i]*x+c[i];
}
double check(double x)
{
	double ret=-1e9;
	for(i=1;i<=n;i++) ret=max(ret,calc(i,x));
	return ret;
}
const double eps=1e-11;
int main()
{
	cout<<fixed<<setprecision(4);
	cin>>t;
	while(t--)
	{
		cin>>n;
		for(i=1;i<=n;i++) cin>>a[i]>>b[i]>>c[i];
		double l=0,r=1e9,ans=0;
		while(r-l>eps)
		{
	//		cout<<l<<" "<<r<<endl;
			double mid1=l+(r-l)/3.000,mid2=r-(r-l)/3.000;
			if(check(mid1)<=check(mid2)) r=mid2-eps,ans=check(mid1);
			else l=mid1+eps;
		}
		cout<<ans<<endl;
	}
	return 0;
}