hdu 2899 二分法+数学！！！

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#include<stdio.h>#include<math.h>#define d 1e-7double f(double x,double y){    return 6*pow(x,7.0)+8*pow(x,6.0)+7*pow(x,3.0)+5*pow(x,2.0)-y*x;}double g(double x,double y){    return 42*pow(x,6.0)+48*pow(x,5.0)+21*pow(x,2.0)+10*x-y;}int main(){    int n;    scanf("%d",&n);    while(n--)    {        double l,r,y,m;        scanf("%lf",&y);        l=0;r=100;        while(r-l>d)        {            m=(r+l)/2;            if(g(m,y)>0)                r=m;            else                l=m;        }            printf("%.4f\n",f(m,y));    }    return 0;}