221 例:求阶方阵A=315的逆矩阵 323 解:|A|=1,M1=-7,M12=-6,M13=3, M,=4,Mn=3,M 22 2. 则 A=A A4 12 2 13 21 7-49 22 63-7 13 23 3 32-4例：求3阶方阵 的逆矩阵. 2 2 1 3 1 5 323 A     =       解：| A | = 1， 11 12 13 21 22 23 31 32 33 7, 6, 3, 4, 3, 2, 9, 7, 4, M M M M M M M M M = − = − = = = = − = = = − 则 11 21 31 1 * * 12 22 32 13 23 33 1 | | A A A A A A A A A A A A A −     = = =       11 21 31 12 22 32 13 23 33 M M M M M M M M M   −   = − −     −   7 4 9 6 3 7 3 2 4   − −   = −       −