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.

 1 #include <iostream>
 2 using namespace std;
 3
 4 double f(double x)
 5 {
 6     return x*x*x - 2*x - 5;
 7 }
 8
 9 int main()
10 {
11     double left = 2.0, right = 3.0;
12     double mid;
13     while(right - left > 0.01)
14     {
15         mid = (right + left)/2;
16         if(f(mid) == 0)
17             break;
18         if(f(mid)*f(left) > 0)
19             left = mid;
20         else
21             right = mid;
22     }
23     cout<<mid<<endl;
24     return 0;
25 }