Question 1135980: Find the standard form of the equation of the parabola with a focus at (7, 0) and a directrix at x = -7.
choices below
y = one divided by twenty eight x2
x = one divided by twenty eight y2
-28y = x2
y2 = 14x
Answer by MathLover1(20850)   (Show Source):
You can put this solution on YOUR website! given:
a focus at ( , ) and a directrix at 
since the vertex, exactly between the focus and directrix, must be at ( ,  ) = ( ,)
the absolute value of  is the distance between the vertex and the focus and the distance between the vertex and the directrix. (The sign on  tells me which way the parabola faces.) Since the focus and directrix are units apart, then this distance has to be one unit, so 
Since this is a "sideway" parabola, then the  part gets squared, rather than the  part. So the conics form of the equation must be:
 ...plug in  and coordinates of the vertex (,)
 => your answer
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