用初等变化法求矩阵A=?的逆矩阵.用初等变化法求矩阵A＝ 1 3 －5 70 1 2 30 0 1 20 0 0 1 的逆矩阵.1 3 -5 70 1 2 30 0 1 20 0 0 1题目是这样的

1 3 -5 7 | 1 0 0 0
0 1 2 3 | 0 1 0 0
0 0 1 2 | 0 0 1 0
0 0 0 1 | 0 0 0 1
1 0 -11 -2 | 1 -3 0 0
0 1 2 3 | 0 1 0 0
0 0 1 2 | 0 0 1 0
0 0 0 1 | 0 0 0 1
1 0 0 -24 | 1 -3 -11 0
0 1 2 3 | 0 1 0 0
0 0 1 2 | 0 0 1 0
0 0 0 1 | 0 0 0 1
1 0 0 0 | 1 -3 -11 -24
0 1 2 3 | 0 1 0 0
0 0 1 2 | 0 0 1 0
0 0 0 1 | 0 0 0 1
1 0 0 0 | 1 -3 -11 -24
0 1 0 3 | 0 1 -2 0
0 0 1 2 | 0 0 1 0
0 0 0 1 | 0 0 0 1
1 0 0 0 | 1 -3 -11 -24
0 1 0 0 | 0 1 -2 -3
0 0 1 2 | 0 0 1 0
0 0 0 1 | 0 0 0 1
1 0 0 0 | 1 -3 -11 -24
0 1 0 0 | 0 1 -2 -3
0 0 1 0 | 0 0 1 -2
0 0 0 1 | 0 0 0 1
故逆矩阵
1 -3 -11 -24
0 1 -2 -3
0 0 1 -2
0 0 0 1
求逆矩阵我还是喜欢用求伴随矩阵的方法，初等变换容易搞错

1 3 -5 7 1 0 0 0
(A,E)=( 0 1 2 3 0 1 0 0 )
0 0 1 2 0 0 1 0
0 0 0 1 0 0 0 1


1 0 0 0 1 -3 11 -20
→(E,B)=( 0 1 0 0 0 1 -2 1 )
0 0 1 0 0 0 1 -2
0 0 0 1 0 0 0 1
则B就是A的逆矩阵

1 3 -5 7 1 0 0 0
0 1 2 3 0 1 0 0
0 0 1 2 0 0 1 0
0 0 0 1 0 0 0 1
1 3 -5 0 1 0 0 -7
0 1 2 0 0 1 0 -3
0 0 1 0 0 0 1 -2～
0 0 0 1 0 0 0 1
1 3 0 0 1 0 5 -17
0 1 0 0 0 1 -1 -1
0 0 1 0 0 0 1 -2
0 0 0 1 0 0 0 1
1 0 0 0 1 -3 8 -14
0 1 0 0 0 1 -1 -1
0 0 1 0 0 0 1 -2
0 0 0 1 0 0 0 1
1 -3 8 -14
0 1 -1 -1
0 0 1 -2
0 0 0 1