Eliot Gable thinks this is interesting: a12x1 From CHAPTER 1 Systems of Linear Equations and Matrices from Elementary Linear Algebra, 11th Edition by Chris Rorres, Howard Anton Publisher: John Wiley & Sons Released: November 2013 Note This is incorrect. Should be a22x1. Share this highlight http://www.safaribooksonline.com/a/elementary-linear-algebra/10317224/ Twitter Facebook Google Plus Email Get Instant Access Now Start a Free Trial Have an account? Sign in. Minimise Unlock the rest of Elementary Linear Algebra, 11th Edition and 30,000 other books and videos By clicking this box, you confirm that you have read and agree to the terms and conditions of our Membership Agreement, and you understand that when your trial period ends, you will be required to provide billing information if you wish to continue using the service. Unlock the rest of this book Start a Free 10-Day Trial loading Learn about Safari for Business Have an account? Sign in.