# When will i come across it

1. Jun 5, 2012

### pcm

a(x2+y2)+bz2=c

what is the shape of the surface for different values(+ve, -ve) of a,b,c.
i wanted to know in which class i will come across these things.
i found this while solving a physics problem and i have no idea about the shape of given surface.

2. Jun 5, 2012

### Jorriss

Perhaps it would help to rearrange it a bit.

a'(x^2+y^2) = c' -z^2

And then, maybe to start, see what it looks like for z=0, 1 and, say, 2.

Last edited: Jun 5, 2012
3. Jun 5, 2012

### pcm

ok so for positive a',b',c'
as i go up the z axis the radius of the circle goes on decreasing.
so what is the shape?
same idea should work for other signs of a,b,c

Last edited: Jun 5, 2012
4. Jun 5, 2012

Hi pcm,