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View Full Version : Find the vertex, focus, and directrix of the parabola given by the equation.


beerxaano
Jun 30, 2009, 11:17 AM
(x-9)^2=-(y+8)?

galactus
Jun 30, 2009, 12:28 PM
There are similar posts. Search those.

Know that (x-h)^{2}=\pm 4p(y-k)

where (h,k) are the coordinates of the vertex.

p is the distance between the focus and vertex or between the vertex and the directrix.

If the sign is negative, then it opens in the negative y direction.

In this case, 4p = -1. You can easily find p now and the focus and directrix from the vertex coordinates.