Exercise 7 3 4 Let A be an m x n matrix of rank k If B is an invertible mxm matrix try to argue why B A is also rank k Using your above logic Suppose that A VW is a matrix with rank k Suppose that B W W is A V W is rank k What does this tell us about elementary row matrices E and rank k matrices A an invertible matrix then explain why B Using your above logic that they operate on