A rectangular matrix is in echelon form if
- If there are any, all zero rows are at the bottom
- The first non-zero entry (leading entry) of a row is to the right of any leading entries in the row above it
- All elements below a leading entry are zero
For reduced row echelon form - All leading entries, if any, are equal to 1.
- Leading entries are the only nonzero entry in their respective column.
Pivot
- A Pivot in a matrix A is a location in A that corresponds to a leading 1 in the RREF of A
- A Pivot column is the column of the pivot
Free Variable
Free variables are the variables of the non-pivot columns
- Any choice of the free variables leads to a solution of the system
- If you have any free variables you do not have a unique solution]
