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May 21st, 2009, 05:15 AM   #1
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Linear Algebra - Singularity problem

Hi all, I'm having a little trouble with a simple question:
I have to proof that if A is singular, and B is not, then AB is singular
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May 21st, 2009, 07:20 AM   #2
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Re: Linear Algebra - Singularity problem

Hint: A matrix is singular iff
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May 21st, 2009, 10:55 AM   #3
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Re: Linear Algebra - Singularity problem

Actually I'm trying to prove that det(AB) = det(A)*det(B), so I can't use this equation and, naturally, have to start by the case where A or B or both are singular...
still looking for an answer, or a hint
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May 21st, 2009, 11:03 AM   #4
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Re: Linear Algebra - Singularity problem

If is nonsingular, then there exists such that What can you then say about
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May 21st, 2009, 11:16 AM   #5
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Re: Linear Algebra - Singularity problem

hmmm
then (BX) would be equal to A^(-1), but wait a minute, A was not supposed to have an inverse, since its singular!
mattpi, you're a genious!!!! sorry for bothering you with this trivial question. =D
see you soon, probably I'll be back with more trivial questions!
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