Which matrix is in reduced echelon form or only in echelon form?

Question

Which matrix is in reduced echelon form and which others are only in echelon form.

Is matrix 1 in reduced echelon form, echelon form only, or neither?

Is matrix 2 in reduced echelon form, echelon form only, or neither?

Is matrix 3 in reduced echelon form, echelon form only, or neither?

1. [1 0 1 0

0 1 1 0

0 0 0 1]

2) [1 0 0 0

0 6 0 0

0 0 1 1]

3) [1 4 0 0

0 0 1 0

0 0 0 0

0 0 0 1]

Answer 1

The first one is reduced row echelon form since the leading entry on all the rows is 1 and it is in row echelon form since the leading coefficient in a given row (first nonzero term) is always to the right of the one in the row above it.

The second has the same reasoning as the first, but the first nonzero term of the second row is 6, and not 1, so it is not in reduced row-echelon form.

For the same reason as the first one, the third one is also in reduced row echelon form.