#include <stdio.h>
#include <conio.h>
#include <math.h>
#define PRECISION 0.01
#define MAX_Number 100

float f(float x) //函數fx)
{
 return(x*x*x-2*x*x-4*x-7);
}

float df(float x)  //函數f(x)的導數f'(x)
{
  return(3*x*x-4*x-4);
  }
  
  
  void NewtonIterative()
  {
  int k;
  float x0,x;
  
  printf("\n\nInput Initial Value:\nx0=");
  scanf("%f",&x);
  k=1;
  do{
    x0=x;
    x=x0-f(x0)/df(x0);
    printf("\nx%d=%f",k,x);
    ++k;
    }while(fabs(x-x0)>PRECISION&&k<MAX_Number);
    
    if(k>=MAX_Number)
      printf("Simple Iterative failed(k=%d)",k);
    else
      {
         printf("\n\nIterative times k=%d",k);
         printf("\nRoot x=%f",x);
      }
  }
  
  
  
  int main()
  {
    NewtonIterative();
  
  
    printf("\n\nPress any dey to quit! \n");
    getch();
  }