Question 816785
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
A line passes through the points (p, a) and (p, –a) 
where p and a are real numbers and p &#8800; 0
(p, a) and 
(p, –a)   m = {{{(a-(-a))/(p-p)}}}  Cannot divide by ZERO, there is no slope to this Line.
slope of the line:  no slope (does not exist)
equation of the line:   x = p  Perpendicular Line
y-intercept: none
slope of a line perpendicular to the given line:  would be m = 0, horizontal Line y = 3, For example
See Lines x = 2 (Blue) and y = 3 (Green) on graph below
{{{drawing(300,300,   -6, 6, -6, 6, blue(line(2,6,2,-6)), grid(1), 

graph( 300, 300, -6, 6, -6, 6, 0, 3))}}}