Those two formulae can be expanded to cases when there are more than two vectors. In addition, for two linear transformations, their effects can be added, i.e., (T + S)(u) = T(u) + S(u).
Those two formulae can be expanded to cases when there are more than two vectors. In addition, for two linear transformations, their effects can be added, i.e., (T + S)(u) = T(u) + S(u).