Spans

In mathematics, the linear span of a set S of vectors (from a vector space), denoted span(S), is defined as the set of all linear combinations of the vectors in S.

$\vec{a}$ is span of $\vec{b}$ and $\vec{c}$ if $\vec{a}=k_1\vec{b}+k_2\vec{c}$ where $k_1$ and $k_2$ are constants.