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Vertex of a Function

  1. Sep 29, 2013 #1

    Drakkith

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    Staff: Mentor

    I have the following function and I'm supposed to find the vertex of its graph.

    f(x)=-3(x-2)2-3

    Why is the vertex (2,-3) instead of (-2,-3)?

    Edit: Bah, nevermind. I just realized the formula has (x-h) in it, not (x+h) in it...
     
    Last edited: Sep 29, 2013
  2. jcsd
  3. Sep 30, 2013 #2

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    Do you understand why the formula for vertex involves x- h, not x+ h?

    The crucial point is that if x= 2, (x- 2) will be 0 so that f(2)= -3. If x is any other number (including -2) x- 2 will NOT be 0 so that, because the square of any non-zero number is positive, -3(x-2)^2 will be negative and f(x)= -3(x- 2)^2- 3 will be lower than three. (2, -3) is the highest point on the graph.
     
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