// diedai.cpp : Defines the entry point for the console application.
//
//第104頁24題：用牛頓法求方程的根
#include "stdafx.h"
#include "iostream.h"
#include "math.h" 

float fun(float x)
{
	float m;
	m=x-(x*x*x+2*x*x+10*x-20)/(2*x*x+4*x+10);
	return m;
}

int main(int argc, char* argv[])
{
	int k=0,N;
	float x0,x1;
	x0=1.0;
	cout<<"求方程x*x*x+2*x*x+10*x-20=0的根"<<endl;
	cout<<"輸入需要迭代的次數(shù)：";
	cin>>N;
	for(;k<=N;k++)
	{
		x1=fun(x0);	
		if(fabs(x1-x0)<0.000001)
			break;
		x0=x1;
	}
	cout<<"求出的根為x="<<x1<<endl;
	return 0;
}