1. The problem is to sketch the graph of the function $y = 18$. 2. This is a constant function where the output value is always 18 regardless of the input $x$. 3. The formula for a constant function is $y = c$, where $c$ is a constant number. 4. Important rule: The graph of a constant function is a horizontal line crossing the $y$-axis at $y = c$. 5. For $y = 18$, the graph is a horizontal line passing through the point $(0, 18)$. 6. This line has no $x$-intercepts because it never crosses the $x$-axis. 7. The $y$-intercept is at $(0, 18)$. 8. There are no extrema (maximum or minimum points) because the function is constant. Final answer: The graph of $y = 18$ is a horizontal line crossing the $y$-axis at 18.