let's say "c" is a constant, hmmmm any constant, for any value whatsoever of "x", "y" is always that constant, for example, say c = 3, thus y = 3, so a table for it will look like
[tex]\bf \begin{array}{ccll}
x&y\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
-\infty&3\\
-6&3\\
-5&3\\
-4&3\\
-3&3\\
-2&3\\
-1&3\\
0&3\\
1&3\\
2&3\\
3&3\\
4&3\\
5&3\\
6&3\\
+\infty&3
\end{array}[/tex]
now, if you plot those points, it'd looks like the picture below.