题目：
(Ⅰ)设A是m×n矩阵，β是任一个m维列向量，证明方程组Ax=β有解的充分必要条件是秩r(A)=m．
(Ⅱ)
答案：
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参考答案：D
(Ⅰ)设A是m×n矩阵，β是任一个m维列向量，证明方程组Ax=β有解的充分必要条件是
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