Question 1171333: Given the parabola
(x+2)^2=-8(y-5), which of the following is the vertex and directrix?
The directrix is y=0 and the vertex is (-2,5)
The directrix is y=-4 and the vertex is (-2,5)
The directrix is y=7 and the vertex is (-2,5)
The directrix is y=3 and the vertex is (-2,5)
Found 2 solutions by Edwin McCravy, greenestamps:
Answer by Edwin McCravy(20054)   (Show Source):
Answer by greenestamps(13198)  (Show Source):
You can put this solution on YOUR website!
The given equation is in vertex form,
where the vertex is (h,k) and p is the directed distance from the directrix to the vertex.
With the given equation, then, you can see immediately that the vertex (h,k) is (-2,5) and 4p=-8 so p is -2.
Since p is the directed distance from the directrix to the vertex, p=-2 means the directrix is 2 units ABOVE the vertex, because it is 2 units down from the directrix to the vertex. So the directrix is at y=5+2=7.
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