#include<iostream.h>
#include<math.h>
#define N 100
#define EPS 1e-6
#define ETA 1e-8

void main()
{
	float f(float);
	float f1(float);
	float x0,y0;
	float Newton(float (*)(float),float (*)(float),float);
	
	cout<<"Please input x0\n";
	cin>>x0;
	cout<<"x(0)="<<x0<<endl;
	y0=Newton(f,f1,x0);
	cout<<"\nThe root of the equation is x="<<(float)y0<<endl;
}

float Newton(float (*f)(float),float (*f1)(float),float x0)
{
	float x1,d;
	int k=0;
	do{
		x1=x0-f(x0)/f1(x0);
		if((k++>N)||(fabs(f1(x1))<EPS))
		{
			cout<<"\nNewton method faild!";
				return 0;
		}
		d=(fabs(x1)<1?x1-x0:(x1-x0)/x1);
		x0=x1;
		cout<<"x("<<k<<")="<<x0<<endl;
	}
	while(fabs(d)>EPS&&fabs(f(x1))>ETA);
	return 1;
}

float f(float x)
{
//	return log(x)+x-2;
	return x*x*x+x*x-3*x-3;
}

float f1(float x)
{
//	return 1/x+1;
	return 3.0*x*x+2*x-3;
}