Question

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

Answer 1

First of all the slope is a number that tells you how steep is your line and in what direction, upwards or downwards.

You can see that your function, or the line representing it, is neither up nor down...it is constant. As a consquence its slope cannot be positive or negative...the only possible option is zero. Your slope is then zero or, in other words, your line is perfectly horizontal.

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:
`slope=(Deltay)/(Deltax)=(y_2-y_1)/(x_2-x_1)`
As you can see in your function is always `Deltay=0`