If $A$ and $B$ are two conformable matrices,and $AB = A$ and $BA = B$ then prove that A and B are idempotent matrices.
This may be trivial but I am not sure how to proceed on this.
$$Ax = ABx = A(BA)x = (AB)Ax = AAx$$
Sign up using Google
Sign up using Facebook
Sign up using Stack Exchange
4 years ago