A linear transformation is surjective if and only if the columns of its matrix span the codomain.

Created almost 9 years ago, updated about 8 hours ago

Let $A=[T]_{C\leftarrow B}$. The map $T:V\to W$ is surjective iff its matrix columns span the entire coordinate space of $W$, iff $\operatorname{rank}A=\dim W$. A pivot in every row tests this. Independence of columns instead tests injectivity.

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