Answer: The slope is undefined.
Explanation:
Using the formula given, find the difference in the y coordinates of the points and divide it by the x coordinates.
(3,6)
(3,-3)
y coordinates: 6 - (-3) = 9
x coordinates: 3- 3 = 0
9/0 = undefined.
Any number being divided by 0 is undefined because you can't divide something by anything.
Also remember that if a line is vertical through any of the x coordinate, the slope will always be undefined and the equation of line is x = 3