Answer:
Undefined
Explanation:
Given any two points (x1, y1) and (x2, y2), the slope of the line is calculated using the formula:

Let (x1, y1) = (-8,-1) and (x2, y2)=(-8,-11).
Substitute:

Since division by 0 is not possible, the slope of the line that passes through (-8, -1) and (-8, -11) is undefined.
In general, the slope of any vertical line is undefined.