Linear Equations and Spreadsheets

In many applications of linear algebra a key element is often the solution of the linear equations MX = B. When the matrix M is non-singular, this presents no problem with the help of general-purpose software such as computer algebra or a spreadsheet. However, when M is singular or non-square, finding a solution may demand a computer program or specialist software. A method for solving MX=0 in all cases is described in this note and illustrated by a model of traffic at a T-junction. The method employs only array commands widely available on spreadsheets. The worksheet from the spreadsheet Excel (Microsoft Corporation, 1992) in which the model is solved is reproduced. It is proposed that the method exposes the student to ideas and techniques which may be hidden by other software.