SOLUTION: an n *n matrix A is called nilpotent if, for some positive integer k, A^k = o, where o is the n*n zero matrix. Prove that id A is nilpotent, the det A = 0.

Algebra ->  College  -> Linear Algebra -> SOLUTION: an n *n matrix A is called nilpotent if, for some positive integer k, A^k = o, where o is the n*n zero matrix. Prove that id A is nilpotent, the det A = 0.      Log On


   



Question 1200894: an n *n matrix A is called nilpotent if, for some positive integer k, A^k = o, where o is the n*n zero matrix. Prove that id A is nilpotent, the det A = 0.
Answer by ikleyn(52817) About Me  (Show Source):
You can put this solution on YOUR website!
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For any matrix A,  det%28A%5Ek%29 = %28det%28A%29%29%5Ek.


If A is a nilpotent matrix, then  A%5Ek = 0;  hence  %28det%28A%5Ek%29%29 = 0.


It implies that for nilpotent matrix A  %28det%28A%29%29%5Ek = 0  for some integer k > 0;  hence,  det(A) = 0.    QED

Solved.