HDU 2899 Strange fuction(牛顿迭代)

#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
const double eps = 1e-9;
double y;
double fdd(double x) {
    return 252 * pow(x, 5) + 240 * pow(x, 4) + 42 * x + 10;
}
double fd(double x) {
    return 42 * pow(x, 6) + 48 * pow(x, 5) + 21 * pow(x, 2) + 10 * x - y;
}
double f(double x) {
    return 6 * pow(x, 7) + 8 * pow(x, 6) + 7 * pow(x, 3) + 5 * pow(x, 2) - y  * x;
}
double Newton(double x) {
    while(fabs(fd(x)) > eps) 
        x = x - fd(x) / fdd(x);
    return x;
}
int main() {
    int QwQ;
    scanf("%d", &QwQ);
    while(QwQ--) {
        scanf("%lf", &y);
        double ans = 1e15, pos;
        for(int i = 0; i <= 100; i++) {
            double anspos = Newton(i);
            if(anspos >= 0 && anspos <= 100) 
                ans = min(ans, f(anspos));
        } 
        printf("%.4lf\n", ans);
    }
    return 0;
}