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Home Q & A Board Science-Related Homework Help Mathematics
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smokin7acehole smokin7acehole
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11 years ago
I was absent on the day we learned this and I can't really understand what to do from the things I've found online.

How do you find the directrix of a parabola with the equation y=(x+4)^2-8

How do you find the vertices of this ellipse:  ((x+1)^2)/(9) + ((y-4^2)/(25)=1

Thank you
it should be (y-4)^2, not y-4^2.
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#1
11 years ago
Always go by understanding the geometry than trying to memorize the algebra:

1)  The directrix is perpendicular to the parabola's axis of symmetry, and is the same distance from the vertex as the focus is.

2)  In the ellipse, find the center and the length of the major axis (call this length M).  A vertex is distance M upward, or to the right of, the center, accordingly as the major axis is oriented vertically or horizontally.
Answer accepted by topic starter
hunterpryorhunterpryor
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#2
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11 years ago
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