In order to find the slope, we have the formula is
The change of Y (Also Y minus each other)
----------------------------------------------------------------- Over (As fraction
The change of X (Also X minus each other)
Now the first point is (1,10) The Y is 10
The X is 1
Now the Second Point is (1,-8) The Y is -8
The X is 1
So now we plug the numbers in
10-(-8)
--------- which is equal to 18/0
1-1
A quick tip is that you CAN'T divide by zero
Therefore the answer is unidentified, but now you know how to solve for slopes