Posted by Verti on Tuesday, November 25, 2008 at 5:06pm.
How do you find the standard equation for a parobala when you do not have the directrix? I do have the focus, but the thing is the focus is not a 0,p value, it is 2,5, so I don't see how it could really be a focus. I'm sorry I can't get the graph in this message, but an explanation on finding the standard equation in general will do. Thanks!!!

Algebra  Reiny, Tuesday, November 25, 2008 at 5:36pm
<< ...but the thing is the focus is not a 0,p value, it is 2,5...>>
Is the focus (0,2.5) or (2.5,0)
you are also missing some more information.
There has to be at least another point given on the parabola.
Did they perhaps give you the vertex?
Here is a nice webpage that explains a lot about the parabola and its variations of equations to express it.
http://www.algebralab.org/lessons/lesson.aspx?file=Algebra_conics_directrix.xml