An elementary matrix is a special type of matrix that results from performing a single elementary row operation on an identity matrix. Elementary matrices are useful in linear algebra, particularly in the context of solving systems of linear equations, performing Gaussian elimination, and understanding matrix inverses. There are three types of elementary row operations, each corresponding to a type of elementary matrix: 1. **Row Switching**: Swapping two rows of a matrix.
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An elementary matrix is obtained by applying one elementary row operation to the identity matrix. Multiplying by it on the left performs the same row operation on . Such a matrix is invertible: reverse a row swap, reverse a nonzero row scaling by its reciprocal, or reverse adding a multiple of another row by adding its negative. Right multiplication gives an elementary column operation. In particular these operations preserve matrix rank.