How To Study As A Mathematics Major
《How To Study As A Mathematics Major》 · 第 8 页 · Section 0.2.7「Nullspace, range, row space, and column space」
The range of $A\in M_{m,n}(F)$ is also called its column space because $Ax$ is a linear combination of the columns of $A$ for any $x\in F^n$ (the entries of $x$ are the coefficients in the linear combination); $\operatorname{range}A$ is the span of the columns of $A$.