Ok so I have the question and answer but need to be explained why the answer works.
1 answer:
As you know the directrix and focus. so first of all find the distance 'a.f' shown in the figure. now find the location of the mid point of the line 'a.f' because it's the vertex. half the distance to get the focal length 'a'. now put all the values in the equation given to get the equation of required parabola.
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