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 yaxis?
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, 1sqrt5/2)?

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