快速弦截法求解方程

#include <iostream>
using namespace std;
void main()
{
float x0,result,e;
float f(float x);
float f1(float x);
float quick(float (*f)(float),float x0,float e);
cout<<"输入初始值：";
cin>>x0;
cout<<"输入精度：";
cin>>e;
result=quick(f,x0,e);
cout<<"运算结果是："<<result<<endl;
}
float quick(float (*f)(float),float x0,float e)
{
float x1=x0+f(x0),x2;
x2=x1-f(x1)*(x1-x0)/(f(x1)-f(x0));
while(x1-x2>=e || x2-x1>=e)
{
  x0=x1;
  x1=x2;
  x2=x1-f(x1)*(x1-x0)/(f(x1)-f(x0));
}
return x2;
}
float f(float x)       [url=file://要/]file://要[/url]解的方程为f(x)=0
{
return x*x-x-12;
}