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Homework Help: PRoblems with precalc functions

  1. May 27, 2007 #1
    I'm trying to find where this function increases and decreases:

    f(x) = = - x^2 - 6x - 8

    I can get the vertex (h, k), which works out [by my math] to be (3, -17).

    I'm just not sure where to go from here to get information like:
    point of increase and decrease
    domain and range

    Thanks for any help!
    Last edited: May 27, 2007
  2. jcsd
  3. May 27, 2007 #2
    For the vertex, I get (-3,1), using the formula for h=-b/(2a). The vertex is where it switches from increasing to decreasing or from decreasing to increasing. The leading coefficient tells you which of these two cases it actually is...
  4. May 27, 2007 #3
    Aaah... I see what I did wrong, I simply forgot that a=-1, I was thinking a=1.

    When I set a to -1 instead of 1 it all works out! Thanks!
  5. Jan 20, 2009 #4
    i need help finding 2 solutions to an equation. cos(theta) = 1/(sq.root of 2)
    thanks !
  6. Jan 20, 2009 #5


    Staff: Mentor

    It's considered bad form to "hijack" an existing thread with a new question.

    You should start a new thread.
  7. Jan 20, 2009 #6
    im sorry ! its my first time using forums and all that stuff. my bad, but can anyone help me ?
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