Math 152 2017 Question A13

I think that "reduced row echelon form" means that the first "1" in each row has to come after the first "1" in the previous row, so the matrix appearing in the hint of that problem is not in reduced row echelon form.

In fact, any invertible matrix has the identity as its reduced row echelon form: a standard algorithm to invert an invertible matrix is to augment the matrix by the identity and write the resulting matrix in reduced row echelon form; the left half of the matrix will then be the identity matrix.

If you think I've made a mistake, please let me know.

thanks！i think you are right. i have corrected it.