If A is an n x n matrix and the homogeneous system ATx = 0 has a unique solution,
what can you say about the dimension of the row space and column space of A?
Suppose A is an m x n matrix of rank r, and E is an n x m elementary matrix.
Let B = EA, indicate whether each statement is true or false.
(a) A and B have the same null space
(b) A and B have the same column space
(c) A and B have the same bases for row space