# How do you determine the slope of y=16?

Another way to see it is to say that the slope is a measure of how the value of $y$ changes for each change in the value of $x$, or:
$s l o p e = \frac{\Delta y}{\Delta x} = \frac{{y}_{2} - {y}_{1}}{{x}_{2} - {x}_{1}}$
As you can see in your function is always $\Delta y = 0$