Section 1.2 Elementary Column Operations
Elementary column operations are the column analogue of elementary row operations. Their precise properties can be deduced by applying elementary row operations to the transpose of a matrix and then transposing the result. In particular, if \(F\) is the elementary matrix corresponding to the elementary column operation \(f\) then \(f(A) = AF\text{.}\) Note that, because transposition changes the order of a product, elementary column operations correspond to post-multiplication by an elementary matrix. Two matrices that are related by a sequence of elementary column operations are said to be column equivalent and two matrices \(A\) and \(B\) are column equivalent if and only if there exists a non singular matrix \(Q\) such that \(B = AQ\text{.}\)
Example 1.2.1.
Use the columns operations to find the inverse of the matrix \(\begin{pmatrix}2\amp 1\amp 1\amp 1\\1\amp 0\amp 1\amp 1\\1\amp 1\amp -2\amp 1\\1\amp 1\amp 1\amp -1\end{pmatrix}\) by appending the \(4\times 4\) identity matrix at the bottom and appyling the columns aperation in Sage.
Let us look at how we can achieve this in Sage.