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#1 2007-11-23 07:14:11
- EPhillips1989
- Member
- Registered: 2007-11-03
- Posts: 29
invertible matrices
Let A,B be nxn matrices, such that AB=In
can anyone prove that A is invertible with inverse B
please help!!
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#2 2007-11-23 07:30:53
- mathsyperson
- Moderator
- Registered: 2005-06-22
- Posts: 4,900
Re: invertible matrices
Saying that a matrix X is invertible means that another matrix Y exists such that XY = I. Y is then denoted the inverse of X.
You're given two matrices A, B and told that AB = I, so you can just prove the required results from the definition.
Why did the vector cross the road?
It wanted to be normal.
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#3 2007-11-25 11:15:14
- EPhillips1989
- Member
- Registered: 2007-11-03
- Posts: 29
Re: invertible matrices
thats by definition i was trying to prove this in terms of A,B i dont see how i can apply it??:(
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#4 2007-11-25 11:19:52
- EPhillips1989
- Member
- Registered: 2007-11-03
- Posts: 29
Re: invertible matrices
is this simply enough to write as proof???
(AB)(A)^-1= AA^-1(B)=In(B)
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