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Matrix proof

proof that for any matrices A and B. AB=I implies BA=I

i don't know what to do. any help.
Original post by user6
proof that for any matrices A and B. AB=I implies BA=I

i don't know what to do. any help.


well it is not true in general. Maybe A,B are square matrices?
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Original post by tombayes
well it is not true in general. Maybe A,B are square matrices?


what is a square matrix? anyway surely AB=I obviously implies BA=I
e.g. 3 times 1/3=1=1/3 times 3. Surely AB always is equal BA.
Original post by user6
what is a square matrix? anyway surely AB=I obviously implies BA=I
e.g. 3 times 1/3=1=1/3 times 3. Surely AB always is equal BA.


a square matrix has same number of row and columns. And no for matrices AB is not always equal to BA, can you find an example?

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