Definition:Extended Real Number Line

The extended real numbers is the set of real numbers together with two values, $$\R \cup \left\{{+\infty,-\infty}\right\}$$ where $$+\infty,-\infty \ $$ have the properties


 * 1) $$\forall x \in \R, x < +\infty \ $$
 * 2) $$\forall x \in \R, x > -\infty \ $$

This set is often denoted $$\overline{\R}$$.