/* Newton法 */
/* newton.c */
#include <stdio.h>
#include <math.h>
#define EPS 1.0e-14
#define NMAX 10
double f(double x);
double df(double x);

int main(void)
{
  int n;
  double x,fx,dfx;

  x = 2.0; /* 初期値 */
  n = 0;
  fx = f(x);
  dfx = df(x);
  printf("%3d %20.15f %10.2e\n",n,x,fx);
  while(fabs(fx) > EPS && n < NMAX){
    x = x - fx / dfx; 
    n++;
    fx = f(x);
    dfx = df(x);
    printf("%3d %20.15f %10.2e\n",n,x,fx);
  }

  return 0;
}

double f(double x) /* f(x) */
{
  double y;

  y = -5.0 + x * (- 2.0 + x * x);

  return y;
}

double df(double x)  /* f'(x) */
{
  double y;

  y = -2.0 + 3.0 * x * x;

  return y;
}