>i need to find the equation for a vertical line... strictly
>going up and down, however i am having severe difficulties
>with it... please help

How about x = 3?

I presume what you want is an equation of the form

y = mx + c

However this is not possible for a vertical line: just have a think about it - in the above example, what value does y take at x = 3? It takes many values, but a function can only give a single value for a single input, so y cannot be given as a function of x.

You could also define the line parametrically: for any s,

(x(s), y(s)) = (3, s)

Hope this helps,

Rich