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Homework Help: Calc stationary points question

  1. May 11, 2006 #1
    c and d are positive integers greater than one

    y = (c*e^d) / (x^d +1)

    I need to try and find the co-ordinates for stationary point. apparently the general co-ordinates for the SP are not possible to find and i must explain why?

    help aprectiated

    ohh where i am up to... i think i got x^(d-1) = 0
    wat u guys get?
    Last edited: May 11, 2006
  2. jcsd
  3. May 11, 2006 #2
  4. May 11, 2006 #3


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    What do you get when you differentiate the expression? Do you know chain rule?
  5. May 11, 2006 #4
    i used quotient rule

    [ (x^d +1)(0) - (ce^d)(dx^(d-1)) ] / [ (x^d +1)^2 ]

    = -ce^ddx^(d-1)) / (x^d +1)^2
  6. May 11, 2006 #5


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    That's correct :smile:

    I can only see x=0 for the constraints you give which gives y as...
    Last edited: May 11, 2006
  7. May 11, 2006 #6


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    At a stationary point, either the derivative is 0 or the derivative does not exist. A fraction is 0 only if the numerator is 0 and "does not exist" only if the denominator is 0. What does that tell you about stationary points for this function? What about the value of the function at that value of x?
  8. May 11, 2006 #7
    thanks j77 :)

    HMMm hallsoivy nice thinking, i like it
    stationary points of this function....
    derivative is 0 when -c(e^d)dx^(d-1) = 0.....
    -c(e^d)d cannot = 0,
    so x^(d-1) = 0...and then?

    What about the value of the function at that value of x?
    wats this?
    Last edited: May 11, 2006
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