//用快速弦截法求方程5x*x*x+2*x*x-6=0的根

#include<iostream.h>
#include<math.h>


double f(double x)
{
	return  4*x*x+x-3;
}
void xianjie(double x0,double x1,double l)//l為精度
{
	double x_k0=x0,x_k1=x1,x_k2=x1;
	for(int i=0;i<30;i++)
	{
		x_k2=x_k1-f(x_k1)*(x_k1-x_k0)/(f(x_k1)-f(x_k0));
		if(fabs(x_k2-x_k1)<l||fabs(f(x_k2)<l))
		{	cout<<"x="<<x_k2<<endl;return;}
		else
		{
			x_k0=x_k1;
			x_k1=x_k2;
		}
	}
	cout<<"no root!"<<endl;
}

void main()
{
	cout<<"please input x0,x1,l:"<<endl;
	double x0,x1,l;
	cin>>x0>>x1>>l;
	xianjie(x0,x1,l);
}