简答题\n \n \n \n \n \n \n \n \n \n \n 已知，则( )。\n \n \n \n \n \n \n \n \n \n \n A.\n \n \n \n \n \n \n \n B.\n \n \n \n \n \n \n \n C.\n \n \n \n \n \n \n \n D.\n \n \n \n \n \n \n简答题\n \n \n \n \n \n \n \n \n \n \n 若A为6阶方阵，齐次方程组Ax=0基础解系中解向量的个数为2， 则（ ）。\n \n \n \n \n \n \n \n \n \n \n A.\n 2\n \n \n \n \n \n \n B.\n 3\n \n \n \n \n \n \n C.\n 4\n \n \n \n \n \n \n D.\n 5\n \n \n \n \n \n简答题\n \n \n \n \n \n \n \n \n \n \n 若由AB=AC必能推出B=C（A，B，C均为n阶矩阵）则A必须满足（ ）。\n \n \n \n \n \n \n \n \n \n \n A.\n A≠O\n \n \n \n \n \n \n B.\n A=O\n \n \n \n \n \n \n C.\n \n \n \n \n \n \n \n D.\n \n \n \n \n \n \n简答题\n \n \n \n \n \n \n \n \n \n \n A为n阶方阵，若存在n阶方阵B，使AB=BA=A，则（ ）。\n \n \n \n \n \n \n \n \n \n \n A.\n B为单位矩阵\n \n \n \n \n \n \n B.\n B为零方阵\n \n \n \n \n \n \n C.\n \n \n \n \n \n \n \n D.\n 不一定\n \n \n \n \n \n多选题\n 若矩阵的秩为，则矩阵的所有阶子式均为零。（ ）\n简答题\n 设A为3阶矩阵，A的秩r（A）＝3，则矩阵A*的秩r（A*）＝（ ）。 A、0 B、1 C、2 D、3\n