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Spydur · Oct 15, 2009, 02:34 PM

Okay, these are homework questions that I have, and I am kind of having a hard time with it.
Here it is:
Find the vertex, focus, and directrix of the parabola. Sketch the graph. Showing the focus and the directrix.

2.) 20x=y^2

4.) x^2= -3y

Can anyone help, please? :o

galactus · Oct 16, 2009, 11:29 AM

$x^{2}=-3y$

To graph, solve for y and get $y=\frac{-x^{2}}{3}$

To find the focus and directrix, use $x^{2}=-4py$

because it opens downward.

$-3=-4p$

$p=\frac{3}{4}$

The focus and directrix are 3/4 units above and below the origin.

The directrix is at y=3/4 and the focus at (0,-3/4)

The other one opens to the right. Do the same thing.