Given two points and
, the equation of the line passing through them is
This formula, however, only works if the points don't share any of the two coordinates. Otherwise, one of the two conditions is true:
And at least one of the denominators in the formula above will vanish.
So, if two points share the same x coordinate, they lie on the vertical line x=k, where k is the shared x coordinate.
Similarly, if two points share the same y coordinate, they lie on the horizontal line y=k, where k is the shared y coordinate.
In your case, the x coordinate is the same, so the points lie on the vertical line x=10.