Question 254985
what is the slope of the line x=5

that is a vertical line

vertical lines have undefined slopes

to demonstrate: m=slope=(y2-y1)/(x2-x1) with (x1,y1)=(5,5)
                                              (x2,y2)=(5,0)
m=(0-5)/(5-5)=-5/0, you can not divide by 0, it is an infinite result, or in other words an undefined result