# Talk:Elementary matrix

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Field: Algebra

## Lock

Why is this article locked? — Preceding unsigned comment added by 128.220.31.54 (talk) 19:34, 29 June 2011 (UTC)

## Alternate meaning

Doesn't "elementary matrix" also refer to a matrix E_{ij} consisting of a single entry 1, and the rest 0? 76.126.116.54 (talk) 08:28, 12 December 2008 (UTC)

Dummit and Foote's Abstract Algebra (3rd Ed.) uses the notation $E_{ij}$ as you suggest, but only in an exercise (7.2.6). It doesn't give a name to those matrices, either. It uses them later in exercise 7.3.21 to show that any two-sided ideal of $M_n(R)$ is $M_n(J)$ for a two-sided ideal J of R, but the matrices themselves don't seem terribly important. 67.158.43.41 (talk) 16:04, 27 February 2011 (UTC)

## What is the correspondence? Multiplication from the left.

The article says that the elementary matrices correspond to the elementary row operations but does not mention that if you have any elementary matrix E and take any matrix M with the same number of rows as the number of columns of E, then E*M gives a matrix which has the elementary operation of E performed on the rows of M. To see this, extend the columns of M by an identity matrix with the same number of columns as the number of rows of M. See, e.g. Cliff's notes on this subject Penguian (talk) 00:16, 6 September 2010 (UTC)

You're correct; I've now made this change. Next time, instead of letting it sit for two years, be bold and improve it yourself! :-) Mark M (talk) 17:13, 29 November 2012 (UTC)