Strange fuction HDU 2899 【二分】

Problem Description

Now, here is a fuction:
  F(x) = 6 * x^7+8*x^6+7*x^3+5*x^2-y*x (0 <= x <=100)
Can you find the minimum value when x is between 0 and 100.

 

Input

The first line of the input contains an integer T(1<=T<=100) which means the number of test cases. Then T lines follow, each line has only one real numbers Y.(0 < Y <1e10)

 

Output

Just the minimum value (accurate up to 4 decimal places),when x is between 0 and 100.

 

Sample Input

   
   
   
   

    
    
    
    2
100
200
   
   
   
   

 

Sample Output

   
   
   
   

    
    
    
    -74.4291
-178.8534
   
   
   
   

 

#include <stdio.h>
#include <math.h>
int y;
double fun1(double x)
{
    return 42*pow(x,6) + 48*pow(x,5) + 21*x*x + 10*x - y;
}

double fun2(double x)
{
    return 6*pow(x,7) + 8*pow(x,6) + 7*x*x*x + 5*x*x-y*x;
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&y);
        double left=0,right=100,middle;
        while(right-left>=1e-10)
        {
            middle=(left+right)/2;
            if(fun1(middle)>0) right=middle;
            else left=middle;
        }
        printf("%.4lf\n",fun2(left));
    }
    return 0;
}