Definition of (row) echelon form of a matrix
Definition: The (row) echelon form of a matrix $A$ is any matrix $U$ in row echelon form such that $U$ is row-equivalent to $A$ (i.e., $U$ can be obtained from $A$ by a sequence of elementary row operations).
Key points:
- A matrix can have many echelon forms (depending on the sequence of row operations chosen).
- However, every matrix has exactly one reduced row echelon form (RREF).
- The pivot positions are the same in all echelon forms of a given matrix.
- The echelon form reveals: rank (number of pivots), consistency of the associated linear system, and which variables are free vs. basic.