Question 968899
{{{drawing(400,400,-4,10,-4,10,

graph(400,400,-4,10,-4,10), line(4,-20,4,20),

locate(4,-2,"(4,-2)"), locate(4,8,"(4,8)"),

circle(4,-2,0.15),circle(4,-2,0.13),circle(4,-2,0.11),circle(4,-2,0.09),circle(4,-2,0.07),circle(4,-2,0.05),circle(4,-2,0.03),circle(4,-2,0.01),

circle(4,8,0.15),circle(4,8,0.13),circle(4,8,0.11),circle(4,8,0.09),circle(4,8,0.07),circle(4,8,0.05),circle(4,8,0.03),circle(4,8,0.01) )}}}
<pre>
As we see, the line is vertical.  That means that it has no slope.

That also means that 

every point on the line has its x coordinate equal to 4.

Therefore its equation is simply 
<font size = 6>
x = 4.
</font>
Edwin</pre>