说明：  牛顿迭代法解方程，主程序是一个KR气体方程的例子，程序中使用了牛顿迭代法和matlab自带的solve函数，作比较，差异确实很小；
(The main program is an example of Kr gas equation. In the program, the Newton iteration method and the solve function of MATLAB are used. Compared with each other, the difference is very small;)