Hint 1.4

A matrix is in row echelon form, denoted ref, if:

1. Zero rows at bottom
2. The first nonzero element of each row is to the left of first nonzero element of row below

If the following is also fulfilled we say the matrix is in reduced row echelon form, denoted rref:

3. All pivot elements are equal to 1
4. All columns with a pivot only have zero entries aside from the pivot