#include <stdio.h>
#include <math.h>
 double func (double x);
 double df (double x);
 int main()
{
 double x0,x1;
 double delta=1.0e-5;
  x0=0.5;
 
 
for(;;){
 
 x1=x0-func(x0)/df(x0);
 
  if(fabs(func(x1))<delta){
    printf("答えは%lfです。\n",x1);
    break;
}
   else{
     printf("%lfは答えではありません\n",x1);
 
     x0=x1;
 }
}
  return 0;
}
double func(double x){
double y;
 y=x*x*x*x*x-30*x*x*x*x+300*x*x*x-1200*x*x+1800*x-720;
 return y;
}
 double df(double x){
  double y;
  y=5*x*x*x*x-120*x*x*x+900*x*x-2400*x+1800;
return y;
}
 

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