链接：https://www.luogu.org/problem/show?pid=3382
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
using namespace std;
double l,r;
int n;
const double eps=
1e-7;
double a[
1000];
double f(
double x)
{
double ans=a[
1];
for(
int i=
2;i<=n+
1;i++)
ans=ans*x+a[i];
return ans;
}
int main()
{
scanf(
"%d%lf%lf",&n,&l,&r);
for(
int i=
1;i<=n+
1;i++)
scanf(
"%lf",&a[i]);
double ll=l,rr=r,midx,midy;
while(rr-ll>eps)
{
midx=(
2*ll+rr)/
3;
midy=(ll+
2*rr)/
3;
if(f(midx)<f(midy)) ll=midx;
else rr=midy;
}
printf(
"%.5lf\n",ll);
return 0;
}
