Without multiplying matrices, find bases for the row and column spaces of A:

How do you know from these shapes that A cannot be invertible?

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- February 13th 2011, 09:51 PMalexmahoneBases for row and column spaces
Without multiplying matrices, find bases for the row and column spaces of A:

How do you know from these shapes that A cannot be invertible? - February 14th 2011, 01:39 AMalexmahone
Upon inspection, I find that a basis for the row space of A is (3,0,3) and (1,1,2) while a basis for the column space is (1,4,2) and (2,5,7). Although I'm not sure why...

- February 14th 2011, 04:51 AMHallsofIvy
If we write A= BC, then C maps all of into a subspace of which can, of course, have dimension no larger than 2. B then maps that subspace into a subspace of R^3 which can have dimension no larger than 2. Since A= BC maps into a two dimensional subspace of , it cannot be invertible.

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How do you know from these shapes that A cannot be invertible?