# conic coordinates and equations

• Feb 8th 2010, 06:21 AM
BigGrin
conic coordinates and equations
I have some more problems with conics to work through....

1
What is the equation of the ellipse with foci at (0,-4) and (0,4) and the sum of its focal radii being 10?

2
Identify the following conic. that is, is it a circle, parabola, hyperbola, or ellipse? Show why.

3
Solve the system of equations.

$3x+4y+z=7$
$2y+z=3$
$-5x+3y+8z=-31$
• Feb 8th 2010, 06:41 AM
HallsofIvy
At least show a little effort! For 2 you haven't even given the "following conic".

What formulas do you know for conic sections? How is the focal distance related to the lengths of the axes?
• Feb 8th 2010, 02:01 PM
BigGrin
Quote:

Originally Posted by HallsofIvy
At least show a little effort! For 2 you haven't even given the "following conic".

What formulas do you know for conic sections? How is the focal distance related to the lengths of the axes?

Heh....I'm sure I typed it in, I must have accidentally deleted it. (Worried)

The conic is:
x^2-4y^2-4x-24y=48

As for conic sections, I know that an ellipse is a set of two points,called foci, that, when the sum of distances for point "P" is tabulated results in a constant.
I only know that to find an equation of a conic from the info I gave I have to use the distance formula.
I must admit to being a little lost as to how to do that though.
I think that I divide both sides of the equation by 48, but beyond that I have no idea what to do.....