#include<iostream> #include<algorithm> #include<cmath> using namespace std; double c(double x) { return x*x*x*x*x-15*x*x*x*x+85*x*x*x-225*x*x+274*x-121; } double p(double x){ if(x<0) return -x; return x; } int main() { double l=1.5,r=2.4; while(r-l>1e-7){ double mid=(l+r)/2.0; if(c(mid)>0) l=mid; else r=mid; } printf("%.6lf\n",l); return 0; }