说明：  病态方程组求解的matlab程序，涵盖LU分解、Jacobi迭代、GS迭代、SOR迭代四种方法，通过输入参数M来选去对应的算法。
(Sick Equations matlab program, covering LU decomposition, Jacobi iteration, GS iteration, SOR iterative four methods, through M to choose input parameters to the corresponding algorithm.)