Elementary Row Operations as Matrix Multiplications/Corollary

Theorem
Let $\mathbf X$ and $\mathbf Y$ be two $m \times n$ matrices that differ by exactly one elementary row operation.

Then there exists an elementary matrix of order $m$ such that:


 * $\mathbf {E X} = \mathbf Y$

Proof
Let $e$ be the elementary row operation such that $e \paren {\mathbf X} = \mathbf Y$.

Then this result follows immediately from Elementary Row Operations as Matrix Multiplications:


 * $e \paren {\mathbf X} = \mathbf {E X} = \mathbf Y$

where $\mathbf E = e \paren {\mathbf I}$.