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Homework Help: Need help with conic intersection algebra

  1. Feb 22, 2012 #1
    1. The problem statement, all variables and given/known data

    Find intersection points of the following.(Conics are centered to origin)

    Circle = x^2+y^2=4, Ellipse = (x^2/4)+(y^2/9) = 1

    3. The attempt at a solution

    So far I have this. (BTW I know the solutions are (-2,0) and (2,0) but I'm still unsure how to get there step by step).

    (x^2/4)+(y^2/4) = (x^2/4)+(y^2/9)= 1

    What's the next step?
  2. jcsd
  3. Feb 22, 2012 #2


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    If you have (x^2/4)+(y^2/4) = (x^2/4)+(y^2/9) what do you get if you subtract (x^2/4) from each side?
  4. Feb 22, 2012 #3
    Oh ok, so the answer is 5y^2=1?
  5. Feb 22, 2012 #4


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    Why would you get that? Reread my last post.
  6. Feb 23, 2012 #5
    I'm not sure exactly how to solve this, but I would look at the vertices of the ellipse and the radius of the circle
  7. Feb 23, 2012 #6
    hey cacophony , just plot the two graphs and you will see the intersection
  8. Feb 23, 2012 #7


    Staff: Mentor

    But that will probably not help the OP in identifying the intersection points, which is what the problem asks him/her to do.
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