+ \cdots + x_n \begin{bmatrix}a_{1n}\\a_{2n}\\ \vdots \\a_{mn}\end{bmatrix} = \begin{bmatrix}b_1\\b_2\\ \vdots \\b_m\end{bmatrix} This allows all the language and theory of vector space s (or more generally, module s ) to be brought to bear. For example, the collection of all possible linear combinations of the vectors on the left-hand side is called