Question

How do you find the slope of the line x=9?

Answer 1

Slope`=`indeterminate.

Explanation:

First you see that this equation represents a perfectly vertical line! So the slope will be indeterminate.

To try to evaluate it you can use the definition of slope `m`:
`m=(Deltay)/(Deltax)` but your equation for any `y` will always have `x=9` so `Deltax=0`!!!!
The relationship for the slope `m=(Deltay)/(Deltax)` will then give you a division by zero, which is ideterminate.