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Math

posted by on .

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 - ,

    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 - ,

    Yesterdays post

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

  • Math - ,

    so the vertices would be
    (2, -1+sqrt5/2) (2, -1-sqrt5/2)?

  • Math - ,

    yes

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