文件目录

#include <bits/stdc++.h>
using namespace std;
double getf(double x)
{
    return pow(x, 5) - 15 * pow(x, 4) + 85 * pow(x, 3) - 225 * pow(x, 2) + 274 * x - 121;
}
int main()
{
    double l = 1.5, r = 2.4;
    double mid;
    while (fabs(l - r) > 1e-10)
    {
        mid = (l + r) / 2;
        if (getf(mid) > 0)
            l = mid;
        else
            r = mid;
    }
    printf("%.6lf", mid);
    return 0;
}