練習二分練習練習二分~~~

#include <cstdio>
#include <cstring>
#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;

bool check(double mid)
{
    double f = pow(mid,5)-15.0*pow(mid,4)+85.0*pow(mid,3)-225.0*pow(mid,2)+274.0*mid-121.0;
    if(f > 0.0) return 1;
    return
 
 0;
}

int main()
{
    double l = 1.5, r = 2.4, mid;
    while(r-l > 0.00000001)
    {
        mid = (l+r)/2.0;
        if(check(mid)) l = mid;
        else r = mid;
    }
    printf("%.6lf", mid);
    return 0;
}