太难了，不会搞，帮帮我

太难了，求攻略，在线等

#include<bits/stdc++.h>
using namespace std;
double f(double x)
{
    return x*x*x-5*x*x+16*x-80;
}
int main()
{
    double a,b;
    cin>>a>>b;
    double x=(a*f(b)-b*f(a))/(f(b)-f(a));
    while(fabs(f(x))>=1e-6)
    {
        if(f(x)<0)
           a=x;
        else
           b=x;
        x=(a*f(b)-b*f(a))/(f(b)-f(a));
    }
    cout<<fixed<<setprecision(4)<<x;
    return 0;
}

#include <stdio.h>
double func(double x, double b)
{
    return x * x * x - 5 * x * x + 16 * x - b;
}
int main(int argc, char const *argv[])
{
    double x1 = 0, x2 = 0, x, fx;
    double b = 1;
    double e = 1e-7;
    x = x1;
    fx = func(x, b);
    printf("fx = %lf\n",fx);
    while ((fx > 0 && fx > e) || (fx < 0 && fx < -e))
    {
        // printf("condition :%d\n",((func(x1, b) > 0) ^ (func(x2, b) > 0)));
        if (!((func(x1, b) > 0) ^ (func(x2, b) > 0)))
        {
            if (func(x1, b) > 0)
            {
                x1 -= 1;
                printf("change x1.\n");
            }
            else
            {
                x2 += 1;
                printf("change x2.\n");
            }
        }

        else
        {
            x = (x1 * func(x2, b) - x2 * func(x1, b)) / (func(x2, b) - func(x1, b));
            fx = func(x, b);
            if (!(fx > 0 ^ func(x1, b) > 0))
                x1 = x;
            else
                x2 = x;
        }
        printf("temp: %lf,%lf\n", x1, x2);
    }
    printf("final: %lf,%lf", x, func(x, b));
};