Posted by **Abbey(Please help)** on Tuesday, May 4, 2010 at 5:32pm.

Find the center, vertices, foci, and eccentricity of the ellipse.

9x^2 + 4y^2 - 36x + 8y + 31 = 0

I know the center is (2,-1)

For the vertices I had (3,-1)(1,-1) and the foci (3.8,-1)(.20,-1) and e = 1.80 but I think these are wrong.

- Math -
**Reiny**, Tuesday, May 4, 2010 at 5:51pm
I replied to that question yesterday.

Do you agree with my equation?

Since b > a , aren't the foci on the y-axis?

I had

b^2 = a^2 + c^2

9/4 = 1 + c^2

5/4 = c^2

c = ± √5/2

then e = c/b = (√5/2)/(3/2) = √5/3 or appr. .745

if e > 1 ,like you had, you would have a hyperbola

- Math -
**Reiny**, Tuesday, May 4, 2010 at 5:52pm
Yesterdays post

http://www.jiskha.com/display.cgi?id=1272908984

- Math -
**Abbey(Please help)**, Tuesday, May 4, 2010 at 6:14pm
so the vertices would be

(2, -1+sqrt5/2) (2, -1-sqrt5/2)?

- Math -
**Reiny**, Tuesday, May 4, 2010 at 6:19pm
yes

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