$`f:V \to W`$ の核とは：$`\newcommand{\mrm}[1]{ \mathrm{#1} }\newcommand{\mbf}[1]{\mathbf{#1}}`$$`\quad \mrm{ker}(f) := \{v\in V\mid f(v) = 0 \}`$$`g:U \to V`$ の像とは：$`\quad \mrm{img}(g) := \{v\in V\mid \exists u\in U.\, g(u) = v \}`$ …