# Thread: How do I figure out which equation is shown by this graph?!

1. ## How do I figure out which equation is shown by this graph?!

I need to figure this out before I take my test! HELP!

Here's a link to a picture of the graph: http://i14.photobucket.com/albums/a3...Picture2-9.png

I'm pretty sure a=3, but I'm not sure how to figure out a or c, or the final equation?

My choices are:

a) x^2-y^2=9
b) y^2-x^2=9
c) x^2+y^2=9
d) x^2-y^2=3

How do I figure this out?!

THANKS.

2. Of the choices given three are hyperbolas and one is an ellipse.
Eliminate the ellipse.

Of the three remaining hyperbolas, two open right/left, eliminate them.

3. Originally Posted by Plato
Of the choices given three are hyperbolas and one is an ellipse.
Eliminate the ellipse.

Of the three remaining hyperbolas, two open right/left, eliminate them.

Ok, thanks! C would be the ellipse, so I can eliminate that one. So would A and D open right/left? Since they start with X's?

4. Originally Posted by deathtolife04
Ok, thanks! C would be the ellipse, so I can eliminate that one. So would A and D open right/left? Since they start with X's?
correct

i'd call c a circle, but i guess that's ok