Consider the relation defined by the set of ordered pairs: $\{(8, -4), (4, -2), (2, -1), (0, 0), (2, 1), (4, 2), (8, 4)\}$. To determine if this relation is a mathematical function, inspect the first coordinates. The $x$-value $8$ is paired with both $-4$ and $4$, the $x$-value $4$ is paired with both $-2$ and $2$, and the $x$-value $2$ is paired with both $-1$ and $1$. Because single $x$-values correspond to multiple $y$-values, this relation is not a function. The domain is $\{0, 2, 4, 8\}$, and the range is $\{-4, -2, -1, 0, 1, 2, 4\}$.