SOLUTION: What is the directrix of the parabola with equation -28y = x2? show work please?

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Question 475246: What is the directrix of the parabola with equation -28y = x2? show work please?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
-28y+=+x%5E2 ==> 4c = -28 ==> c = -7 (parabola is facing downward with vertex at (0,0)) ==> directrix is y = 7.