Definition:Extended Real Number Line

Definition
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 $\overline{\R}$.