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矩阵的秩A=1aaaa1aaaa1aaaa1A=1aaaa1aaaa1aaaa1求矩阵的秩

题目详情
矩阵的秩A=1 a a a a1 a a a a 1 a a a a 1
A=1 a a a
a 1 a a
a a 1 a
a a a 1
求矩阵的秩
▼优质解答
答案和解析
|A|
=|1 a a a
a 1 a a
a a 1 a
a a a 1|
=|3a+1 a a a
3a+1 1 a a
3a+1 a 1 a
3a+1 a a 1|
=|3a+1 a a a
0 1-a 0 0
0 0 1-a 0
0 0 0 1-a|
=(3a+1)(1-a)^3
=0
a=-1/3或a=1
1. a=-1/3
A
= 1 -1/3 -1/3 -1/3
-1/3 1 -1/3 -1/3
-1/3 -1/3 1 -1/3
-1/3 -1/3 -1/3 1
秩=3
2. a=1
A=
1 1 1 1
1 1 1 1
1 1 1 1
1 1 1 1
=
1 1 1 1
0 0 0 0
0 0 0 0
0 0 0 0
秩=1
3.a≠-1/3且a≠1
秩=4