说明：  大学研究生教材数值分析的课后习题实验，一共有三段程序代码，分别使用弦割法，牛顿法，抛物线法解几个方程，并进行它们三者之间的比较
(University graduate textbook Numerical Analysis Homework experiment, a total of three sections of the program code, respectively, using the chord secant method, Newton method, parabola method to solve a few equations, and the comparison among them)