题目 ：Problem - 2899 (hdu.edu.cn)
#include <bits/stdc++.h>
using namespace std;
//F(x) = 6*x^7+8*x^6+7*x^3+5*x^2-y*x (0 <= x <=100)
#define F(x, y) (x*(x*(x*(x*(x*(x*(6*x+8)))+7)+5)-y))
double solve(double l, double r, double y){double lm, rm;while(r - l > 1e-7){lm = (2*l+r)/3;rm = (l+2*r)/3;if(F(lm, y)>F(rm, y))l = lm;else if(F(lm, y)<F(rm, y)) r = rm;else l = lm, r = rm;}return F((l+r)/2, y);
}
int main(){int T;double y;scanf("%d", &T);while(T--){scanf("%lf", &y); printf("%.4f\n", solve(0, 100, y));}return 0;
}