说明：  作为《数值计算》课程的小练习，里面有两个小题目，第一个是同一个公式有效和无效算法的对比。第二包含了两个代码，一个从大到小计算方程，另一个从小到大计算方程。保留到小数点后两位，用于观察误差积累带来的影响。
(Exercises as the course of the numerical calculation, there are two small subject, the first one is the same formula valid and invalid algorithm comparison. The second contains two codes, from largest to smallest calculation equation, another small to large calculation equation. Reserved to two decimal places, for the impact of the observation error accumulation.)