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Math Help - Ellipse Question

  1. #1
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    Ellipse Question

    Find the co-ordinates of the centre and foci of the ellipse with equation
    25x^2+16y^2-100x-256y+724=0
    What are the coordinated of its verices and the eqns of the directrices?

    I've managed to manipulate the eqn to this form

    \frac{(x-2)^2}{16}+\frac{(y-8)^2}{25}=1

    Therefore got the centre as (2,8).

    I did vertex, directrix and foci for parabolas but not for an ellipse what are the formula? :s i've tried looking them up on the web but it's all confusing. So far i think

    Directrix= +-\frac{a^2}{c}

    Can someone help me out with just this one ? >.< got a whole load more of em to work through that are similar just im stuck at the first hurdle haha
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  2. #2
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    Quote Originally Posted by Kevlar View Post
    Find the co-ordinates of the centre and foci of the ellipse with equation
    25x^2+16y^2-100x-256y+724=0
    What are the coordinated of its verices and the eqns of the directrices?

    I've managed to manipulate the eqn to this form

    \frac{(x-2)^2}{16}+\frac{(y-8)^2}{25}=1

    Therefore got the centre as (2,8).

    I did vertex, directrix and foci for parabolas but not for an ellipse what are the formula? :s i've tried looking them up on the web but it's all confusing. So far i think

    Directrix= +-\frac{a^2}{c}

    Can someone help me out with just this one ? >.< got a whole load more of em to work through that are similar just im stuck at the first hurdle haha
    Have a look here: Ellipse -- from Wolfram MathWorld

    (You have to scroll down a little bit!)
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