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hdu 2899 (數學+二分)

//函式在0——100,肯定是先遞減後遞增的,所以求導數為0的點,用二分
#include<stdio.h>
double y;
double F(double x)
{
	return ((6*x+8)*x*x*x*x*x*x+7*x*x*x+5*x*x-y*x);
}
double f(double x)
{
	return ((42*x+48)*x*x*x*x*x+21*x*x+10*x-y);
}
int main()
{
	int t;
	double left,right,mid;
	scanf("%d",&t);
	while(t--)
	{
		scanf("%lf",&y);
		left=0.0;right=100.0;
		while(right-left>=0.0000000001)
		{
			mid=(left+right)/2;
			if(f(mid)<=0)left=mid;
			else right=mid;
		}
		printf("%.4f\n",F(left));
	}
	return 0;
}