2
100
200

-74.4291
-178.8534
简单二分+数学：求导后二分找与y最接近的值,此时原函数最小；
#include<stdio.h>
#include<math.h>
double y;
double hanshu(double x)//原函数值 
{
	return 6*pow(x,7)+8*pow(x,6)+7*pow(x,3)+5*pow(x,2)-y*x;
}
double daoshu(double x)//导数值 
{
	return 42*pow(x,6)+48*pow(x,5)+21*pow(x,2)+10*x-y;
}
int main()
{
	int n;
	scanf("%d",&n);
	while(n--)
	{
		scanf("%lf",&y);
		if(y>=daoshu(100))
		printf("%lf\n",hanshu(100));
		double right =100,left=0;
		while((right-left)>=1e-10)//二分 
		{
			double mid=(right+left)/2;
			if(daoshu(mid)>0)
			right=mid;
			else
			left=mid;
		}
		printf("%.4lf\n",hanshu(right));
	}
	return 0;
}