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Find the equaion of the parabola

  1. Apr 20, 2010 #1
    Find the equaion of the parabola having its vertex at the origin , its axis as indicated :



    A ) x-axis : (-4, - 20 )

    b) y - axis : (30,-15 )

    C) y - axis : (-root2,3)



    my answer



    A )

    we have (-4, - 20 ) that mean the focus ( - 20 , 0 )

    now we do comper 4ay = - 20

    = -5



    then the equation is : y2 = 4ax

    = y2 =4(-5) x

    =y2 = -20 x



    ----------------



    I sove only number one beacuse i am not sure from my answer

    help me Are this solving corect or not ?
     
  2. jcsd
  3. Apr 20, 2010 #2
    I want you ?
     
  4. Apr 20, 2010 #3

    Mark44

    Staff: Mentor

    These aren't very clear. I guess you mean the axis of symmetry (x-axis or y-axis) and a point on the parabola.
    Why do you think the focus is at (-20, 0)?
    What equals -5?
    y2 = 4ax is the right equation form, but you don't have the right value for a. The point (-4, -20) should make your equation a true statement, but (-20)2 [itex]\neq[/itex] -20(-4).

    You need to get into the habit of checking your work.
     
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