杭电二分题

 2
100
200 

         -74.4291
-178.8534 

#include<iostream>
#include <iomanip>
using namespace std;
long double fun(double x)
{
	return 42*x*x*x*x*x*x+48*x*x*x*x*x+21*x*x+10*x ;
}
long double fun1(double x,double y)
{
	return 6*x*x*x*x*x*x*x+8*x*x*x*x*x*x+7*x*x*x+5*x*x - y*x ;
}
int main()
{
	int t;
	long double y,hight=100,low=0,mid,k;
	cin >> t ;
	while(t--)
	{
		cin >> y;
		hight=100;
		low=0;
		while(hight - low >1e-8)
		{
			mid=(hight + low)/2;
			k=fun(mid);
			if(k>y)
			{
				hight=mid;
			}
			if(k<y)
			{
				low=mid;
			}
		}
		cout << setiosflags(ios::fixed) ;
		cout << setprecision(4) << fun1(mid , y) << endl;
	}
	return 0;
}

杭电二分题

原文：http://blog.csdn.net/zsc2014030403015/article/details/43272941