Answer:
Undefined
Step-by-step explanation:
(see attached for reference)
in our case, we are given 2 points
(x₁, y₁) = (-9,-6)
(x₂, y₂) = (-9,-10)
immediately we can see that the x-ordinate for both points are the same, which means that if we were to draw a line through both points, it would form a vertical line.
By definition, a vertical line has a slope that is undefined (answer)