最近老师让我对这道题目写出详细解答过程，可是我有困难，请求帮助，谢谢各位哥哥姐姐~ (题目如下）（中英文）
suppose you know that the 3 by 4 matrix A has the vector S=(2,3,1,0) as the only special solution to Ax=0.
(a) What is the rank of A and the complete solution to Ax=0
(b) What is the exact row reduced echelon form Rof A?
(c) How do you know that Ax=b can be solved for all b?
假设你知道一个3排4列的的矩阵A只有一个Ax=0的特别解法 S=（2，3，1，0）
（a）A的rank是什么, 求出Ax=0的complete solution
(b) 求出A的最简梯形形式R
(C) 你怎么知道Ax=b 对所有b都有解
这个就是问题了，拜托各位了！ 下周就要用了，谢谢。
a. r(A) = 3,Ax=0的complete solution = {tS | t： any real number.}b. 100001000010c. since r(A) = 3, so dim{Ax | x in R^4}= 3, i.e. it's an onto. Hence Ax=b has solutions for any y.
