Wednesday, 14 January 2015

linear algebra - Are there non-square matrices that are both left and right invertible?

I am aware that invertible square matrices are left invertible and right invertible, and that the left and right inverses are equal. However, I was wondering whether exists a non square m×n matrice A, so that exist both:




  1. An n×m matrice B so that AB=Im

  2. An n×m matrice C so that CA=In



I just couldn't think of an example nor of a proof that these two conditions provide that A is necessarily square.

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