Constant Function

A constant function is a linear function for which the range does not change no matter which member of the domain is used.  $f\left(x_1\right)=f\left(x_2\right)$  for any $x_1$ and $x_2$ in the domain.

With a constant function, for any two points in the interval, a change in $x$ results in a zero change in $f\left(x\right)$ .

The graph of a constant function is always a horizontal line .