T F T F T F T F T F T F T F True or false (circle T or F). Let 0 denote the zero matrix of the appropriate size. If the matrix equation Ax = 0 with A an nxn matrix and 0 the nxl zero vector has only the trivial solution x = 0 then A is row equivalent to the identity matrix. If the columns of nxn matrix A span R" then they are linearly independent. If the matrix equation Ax = b with A an nxn matrix and b an nxl vector has more than one solution then A is row equivalent to the identity matrix. If nxn matrix A is not invertible then AT is not invertible. If L is an nxn invertible lower triangular matrix then so are L'' and L². If U is an nxn upper triangular matrix then so is UT. An nxn lower triangular matrix L is invertible if and only if all of its diagonal elements are nonzero.