Thread: Rank of 2 matrices Proof.

Hello

Both of the below theorems are listed as properties 6 and 7 on the wikipedia page for the rank of a matrix.

I want to prove the following,

If is an M by n matrix and is a square matrix of rank n, then = .

Apparently this is a corollary to the theorem
If and are two matrices which can be multiplied, then .

which I know how to prove. But I can't prove the first theorem. Any ideas?

What do you assume on ? If it won't work.

girdav, spotted and corrected typo.

You can do a reasoning using linear maps, and the fact that a bijective linear map preserves linear independence.

Originally Posted by girdav

You can do a reasoning using linear maps, and the fact that a bijective linear map preserves linear independence.

Do you know of any sources of a proof?