-4(y+2) = (x-3)^2

I need help finding the vertex, axis, p, focus, and directrix. I'm so blanked out.I cannot remember anything.

This is a parabola with equation

It has the form

Where h and k are the coordinates of the vertex.

It has vertex at (3,-2) and is concave down.

You were wondering what 'p' represented. That is the distance from the focus to the vertex.

To find the focus and directrix of this parabola:

It has the form .

In this case , where

Thus, the parabola opens downward and has focus

The directrix is the horizontal line , which is a distance 1 from the vertex.

I made a mistake on the graph. The directrix should read y = -1.

identify the vertex, focus and the directrix of y=1/24x^2

identify the vertex, focus and the directrix of y=1/24x^2

Please start your own thread. Piggy backing on an old thread is not a good idea.

Notice that it has the form .

Since 1/24 is positive, the parabola is concave up and has vertex at the origin.

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Solve for p. p is the distance from the vertex to the focus and from the vertex to the directrix.
The directrix has equation y=-p and the focus has coordinates (0,p)

x^2 = -36y what is the directrix?

solving for directrix?

1st, you must find the axis in equation x^2 = 4ay, then divide -36 by -4 by the process of canceling.. The answer is 9.. therefore a=9 (the axis is 9)..

2nd you must find the focus.. then you can now solve for the directrix..

Quote:

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Originally Posted by xjessy217x

x^2 = -36y what is the directrix?

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This is a parabola with vertex at the origin and concave down.

As Mr. Woman pointed out, p=9.

Thus, the directrix is 9 units from the vertex.

To see it, graph on a calculator or some other software.

If you do not have a calculator, go here and download the free graphing utility.

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