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Homework Help: Equation of a Parabola Passing Through (2,-2√2) Opening to the Right

  1. Aug 24, 2010 #1
    1. The problem statement, all variables and given/known data
    Write the equation of a parabola passing through the point (2,-2√2) and opening to the right.

    2. Relevant equations
    Parabola with a horizontal axis and vertex (0,0) y^2 = 4cx

    3. The attempt at a solution

    Since the parabola opens right I will use the equation y^2 = 4cx
    I will let x = 2 and y = -2√2
    y^2 = 4c(2)
    (-2√2)^2 = 4c(2)
    2 = 4c(2)
    2 = 8c
    1/4 = c
    y^2 = 4(1/4)x
    y^2 = x

    * The answer in my student solution mannual says the correct answer should be y^2 = 4x. When I graph this, my graphs supports this answer, where did I go wrong?
  2. jcsd
  3. Aug 24, 2010 #2
    Sorry, I figured it out. When i squared my y value, i only squared the √2, giving me 2, instead of squaring -2√2 which would give 8.
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