Hello, uselessjack!
Is there more information?
There are four forms of the parabola, each with its own equation.
I'll derive one of them . . .
Find the equation for the parabola that has its focus on the positive xaxis,
4 units away from the directrix. This is a "vertical" parabola, opening upward.
The focus is at
The directrix is: Code:


*  *
 F
  * +    o     *  
*  (f,0) *
* : *
 * : *
 o V
 (f,2)
 :
 :
   +    +     
4

The equation has the form: .
The vertex is at: .
The value of is: .
The equation is: .