设A为n阶可逆矩阵,A*是A的伴随矩阵.证明 (1)|A*|=|A|n-1; (2)(A*)T=(AT)*; (3)(A*)-1=(A-1)*; (4)(A*)*=|A|n-2A; (5)(kA)

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问题 设A为n阶可逆矩阵,A*是A的伴随矩阵.证明
(1)|A*|=|A|n-1
(2)(A*)T=(AT)*
(3)(A*)-1=(A-1)*
(4)(A*)*=|A|n-2A;
(5)(kA)
选项

答案(1)|A*| =||A|A-1| =|A|n|A-1| =|A|n[*] =|A|n-1. (2)(A*)T =(|A|A-1)T =|A|(A-1)T =|A|(AT)-1 =|AT|(AT)-1 =(AT)*. (3)(A*)-1 =(|A|-1)-1 =[*](A-1)-1 =(A-1)-1 =(A-1)*. (4)(A*)* =|A*|(A*)-1 =[*]=|A|n-2A. (5)(kA)*=|kA|(kA)-1 =kn|A|[*]A-1 =kn-1|A|A-1 =kn-1A*. (6)(AB)*=|AB|(AB)-1 =|A||B|B-1A-1 =|B|B-1|A|A-1 =B*A*

解析 本题考查A的伴随矩阵A*的概念、性质和运算.
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