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Math Help - Looking for help on reversing a limit?

  1. #1
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    Looking for help on reversing a limit?

    I need help looking at this problem.

    \lim_{h\to0}\frac{sqrt(16+h){-4}}{h}

    I'm tasked with finding f(x) and some number, a. I think it's supposed to resemble \frac{f(x)-f(a)}{x-a} but that's not leading me anywhere.

    Isn't sqrt(16) the f(x) in this case with 4 being a? I don't need the derivative, so I think I'm supposed to go backwards. I guess I'm hoping someone might be familiar with this type of problem and could toss me a tip. Thanks at any rate.
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  2. #2
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    Re: Looking for help on reversing a limit?

    Consider the alternative definition of the derivative which is

    lim h-> 0 [f(x+h) - f(x)]/h = f'(x) (i.e. the derivative of f at the point x). From this what can you conclude?
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