Does Row echelon form matrix have only 1s and 0s in the main diagonal? Or does it also have other numbers in the main diagonal?

Also how do i stop the 0 s in the leftmost lower triangle from getting converted to a different number while I am trying to convert the other numbers of the triangle to 0?

Row echelon form has the following characteristics, from the lectures:

- Zero rows at the bottom
- Each row has a pivot, which is the leftmost non-zero entry
- Every pivot to is to the right of the pivot in the row above it.
- The rank is the number of pivot.
- in general, pivots greater than one are allowed. This last point answers your question on whether the diagonals can contain numbers other than 0 and 1.

Reduced row echelon form has all pivots equal to 1 and all numbers above a pivot equal to 0.

While trying to change a matrix to its row echelon form, just make sure that you follow the operations that preserve singularity and you are good.