Find the root of the following equation by chord cutting method, f (x) =x^3-5x^2+16x-80=0

#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
double f(double);      // Represents the abscissa of the intersection x Function of
double xpoint(double,double);   // seek （x1,f（x1））,（x2,f（x2）） The connection between x The intersection of the axes （x,0） Coordinates of
double root(double,double);    // Find interval （x1,x2） The real root of
// perform root To be called xpoint function , perform xpoint To be called f function
int main()
{
    double x1,x2,f1,f2,x;
    do{
        cout<<" Please enter the variable x1,x2 Value ：";
        cin>>x1>>x2;
        f1=f(x1);
        f2=f(x2);
    }while(f1*f2>=0);      // When x1 and x2 The cycle of different signs ends
    x=root(x1,x2);       // Root of solving equation
    cout<<setiosflags(ios::fixed)<<setprecision(7); // Specify the output 7 Decimal place
    cout<<" The root of the equation ："<<x<<endl;
    return 0;
}
double f(double x)  // Calculation f（x）
{
    double y;
    y=x*x*x-5*x*x+16*x-80;
    return y;
}
double xpoint(double x1,double x2)
{
    double y;
    y=(x1*f(x2)-x2*f(x1))/(f(x2)-f(x1));   // call f function
    return y;
}
double root(double x1,double x2)
{
    double x,y,y1;
    y1=f(x1);
    do{
        x=xpoint(x1,x2);
        y=f(x);
        if(y*y1>0){
            y1=y;
            x1=x;
        }
        else
            x2=x;
    }while(fabs(y)>=0.00001);
    return x;
}