That's a vertical line, and it has NO slope!

All equations of the form 

x = a

are vertical lines which are " a " units from the y-axis.

The vertical line whose equation is x = 1 is this green
line below:



The point (4,-2) is this point plotted below:



The line parallel to the vertical line whose
equation is x = 1 which goes through the point
(4,-2) is the blue vertical line below:



Its equation is x = 4.  But neither line has a slope.
Vertical lines are the only kind of lines which have no slope.
All other lines have slopes.

Edwin