Question

How do you find the slope of `(4, 6), (4, 8)`?

Answer 1

The line through `(4,6)` and `(4,8)` has an "undefined" slope.

Explanation:

This is a vertical line; there is no change in the `x` coordinate value;
and since the slope is defined to be `("change in "y)/("corresponding change in "x)` any attempt to evaluate the slope would result in an attempt ot divide by zero.