There is only one way to represent a vertical line as an equation:
[tex]x=d[/tex]
We're given:
Both of the x-coordinates in these points are equal.
This indicates that this is a vertical line.
The x-intercept of a vertical line will always look like [tex](x,0)[/tex], where x is the same x-value as the given points.
[tex]x=3[/tex]
[tex]x=3[/tex]