方程求根

一. 二分法

题目：用二分法求方程x³-2x-5=0在区间【2,3】内的一个实根，要求误差不超过0.01.

#include <iostream>
using namespace std;

double f(double x)
{
    return x*x*x - 2*x - 5;
}

int main()
{
    double left = 2.0, right = 3.0;
    double mid;
    while(right - left > 0.01)
    {
        mid = (right + left)/2;
        if(f(mid) == 0)
            break;
        if(f(mid)*f(left) > 0)
            left = mid;
        else
            right = mid;
    }
    cout<<mid<<endl;
    return 0;
}