(1) | \begin{equation} \forall \, x, y \in X : x + y \in X \end{equation} |
(2) | \begin{equation} \forall \, x, y, z \in X : (x + y) + z = x + (y + z) \end{equation} |
(1) | \begin{equation} \forall \, x, y \in X : f(x, y) \in X \end{equation} |
(2) | \begin{equation} \forall \, x, y, z \in X : f(f(x, y), z) = f(x, f(y, z)) \end{equation} |
(1) | \begin{equation} \forall \, x, y \in X : x y \in X \end{equation} |
(2) | \begin{equation} \forall \, x, y, z \in X : (x y) z = x (y z) \end{equation} |
▶ | D265: Monoid |