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Use the definition f(a)=limit

  1. Nov 2, 2009 #1
    it tells me to use the definition

    f(a)=limit..........f(a+h)-f(a)
    ......h->0.........__________
    ...........................h


    to find the derivative of the given function at the indicated poin.
    f(x)=1/x, a=2



    I dont kno what to do
     
  2. jcsd
  3. Nov 2, 2009 #2

    lanedance

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    Re: derivatives

    its hard to read, try teh tex belwo (click on it)
    [tex] lim_{h \rightarrow 0}\frac{f(a+h) - f(a)}{h} [/tex]

    try subsituting into the limit for your function evaulated at x = a, and x = a+h
     
  4. Nov 2, 2009 #3
    Re: derivatives

    this is how far i got and then i got lost

    [tex]
    lim_{h \rightarrow 0}\frac{a-(a+h)}{h(a+h)(a)}
    [/tex]
    and the answer is supos to be -1/4

    im lost
     
  5. Nov 2, 2009 #4

    lanedance

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    Re: derivatives

    you're not that far off, simplify the top line, then see what you cancel
     
  6. Nov 2, 2009 #5
    Re: derivatives

    thanks i got it
     
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