[Math] Elementary Row/Column Operations and Change of Basis

linear algebra

Let $V$ and $W$ be finite-dimensional vector spaces and let $T:V \rightarrow W$ be a linear transformation between them. I have read that

  1. Performing an elementary row operation on the matrix that represents $T$ is equivalent to performing a corresponding change of basis in the range of $T$, and

  2. Performing an elementary column operation on the matrix that represents $T$ is equivalent to performing a corresponding change of basis in the domain of $T$

Admittedly, this is a rather vague formulation but it's all I have. My question is: Can anyone either explain, or provide a reference to, a precise statement of the relationship between change of basis operations and elementary matrices as described above?

Best Answer

HINT: Let be $\{v_{1}, \dots , v_{n} \}$ a basis of $V$ and $\{w_{1}, \dots , w_{m} \}$ a basis of $W$. If a column of the matrix is $^{T}(a_{1i},a_{2i} \dots, a_{mi})$ it means that $T(v_{i}) = a_{1i}w_{1} + a_{2i}w_{2}\dots + a_{mi}w_{m}$, so, for example, exchanging $\{w_{1},w_{2}, \dots , w_{m} \}$ with $\{w_{2},w_{1}, \dots , w_{m} \}$ will transform the column in $^{T}(a_{2i},a_{1i} \dots, a_{mi})$ and so will be $\forall i$. In this way, you have exchanged the first two rows of the matrix.