Definition: A function of the form
$$\begin{align}
z(x,y) & = c,
\end{align}$$
where $c$ is a number, is called a constant function.
Remark: The graph of a constant function of two variables is a horizontal plane.
Example: The function $z(x,y)=3$ is an example of a constant function.
$$\begin{align}
z(x,y) & = c,
\end{align}$$
where $c$ is a number, is called a constant function.
Remark: The graph of a constant function of two variables is a horizontal plane.
Example: The function $z(x,y)=3$ is an example of a constant function.
