牛顿切线法求方程的根出错无法运行，如何解决？(语言-c++)

Question

#include<iostream>
#include<cmath>
using namespace std;
int f(float x)
{
    float y;
    y=x*x+3*x-4;
    return y;
}
int df(float x)
{
    float y;
    y=2*x+3;
    return y;
}
int main()
{
    float x1,x0;
    x1=0;
    do
    {
        x0=x1;
        x1=x0-f(x0)/df(x0);
    }while(fabs(x1)>=0.00001);
    cout<<"x="<<x1<<endl;
    return 0;
}

这段代码运行后没有输出，为什么啊？

Answer 1

算法有问题

#include <cmath>
#include <iostream>

auto f(float x) -> float
{
    float y;
    y = x * x + 4 * x + 4;
    return y;
}
auto df(float x) -> float
{
    float y;
    y = 2 * x + 2;
    return y;
}

int main()
{
    float x1;
    float x0;
    x1 = 0;
    do
    {
        x0 = x1;
        x1 = x0 - f(x0) / df(x0);
    } while (fabs(x1 - x0) >= 0.00001);

    std::cout << "x=" << x1 << std::endl;

    return 0;
}