UVALive 5009 Error Curves 三分

//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<sstream>
#include<cmath>
#include<climits>
#include<string>
#include<map>
#include<queue>
#include<vector>
#include<stack>
#include<set>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
#define pb(a) push(a)
#define INF 0x1f1f1f1f
#define lson idx<<1,l,mid
#define rson idx<<1|1,mid+1,r
#define PI  3.1415926535898
template<class T> T min(const T& a,const T& b,const T& c) {
    return min(min(a,b),min(a,c));
}
template<class T> T max(const T& a,const T& b,const T& c) {
    return max(max(a,b),max(a,c));
}
void debug() {
#ifdef ONLINE_JUDGE
#else

    freopen("in.txt","r",stdin);
    //freopen("d:\\out1.txt","w",stdout);
#endif
}
int getch() {
    int ch;
    while((ch=getchar())!=EOF) {
        if(ch!=‘ ‘&&ch!=‘\n‘)return ch;
    }
    return EOF;
}


const int maxn=10005;
int a[maxn],b[maxn],c[maxn];
double f(int i,double x)
{
    return a[i]*x*x+b[i]*x+c[i];
}
int n;
double  check(double x)
{
    double maxx=f(1,x);
    for(int i=2;i<=n;i++)
        maxx=max(maxx,f(i,x));
    return maxx;
}
int main()
{
    int t;
    scanf("%d",&t);
    for(int ca=1;ca<=t;ca++)
    {
        //int n;
        scanf("%d",&n);
        double maxx=-(1<<29);
        for(int i=1;i<=n;i++)
        {
            scanf("%d%d%d",&a[i],&b[i],&c[i]);
        }
        double l=0,r=1005;
        const double eps=1e-9;
        while(r-l>eps)
        {
            double ll=(2*l+r)/3;
            double rr=(l+2*r)/3;
            if(check(ll)<check(rr))
                r=rr;
            else l=ll;
        }
        printf("%.4lf\n",check(l));
    }
    return 0;
}