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Homework Help: The function f(x) = e^3x +6x^2 +1 has a horizontal tangent at x =?

  1. Feb 25, 2009 #1
    1. The problem statement, all variables and given/known data


    i cant solve it!
    im really lost. i know you find f''(x) (i got 9e^3x +12) but i dont know where to go from there
    what would i do on my calculator?
     
  2. jcsd
  3. Feb 25, 2009 #2
    to calculate the horizontal tangent you only need to solve for f ' (x) = 0. f '' (x) is used and further derivatives are used to check whether that particular solution of the first equation gives a maxima, minima or an inflexion point.

    Solve 3e^(3x) + 12x = 0
     
  4. Feb 26, 2009 #3

    HallsofIvy

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    Science Advisor

    And that equation you will need to solve numerically, perhaps by graphing it on your graphing calculator and "zooming" in where it crosses the x-axis.
     
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