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Topic: derivatives, limts, prooves
Replies: 1   Last Post: Dec 28, 2012 8:26 AM

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Posts: 132
Registered: 11/27/12
Re: derivatives, limts, prooves
Posted: Dec 28, 2012 8:26 AM
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Again, your notation is all wrong. You do NOT write "f'lnx", that is meaningless. You mean that is f(x)= ln(x), then f'(x)= 1/x.

Also, "lim ln((1/x)(1+u)^(1/u) = 1/x ln lim(1+u)^(1/u)" makes no sense because you not say what variable is going to what value. I think you mean "lim_{u-> 0}".

In that case, 1/x is not changing and is, as far as u is concerned, as constant. You should have learned, when you first learned about limits, that lim_{u->a} c f(u)= c [lim_{u->a} f(u) for any constant c. That is, we can take multiplied constants out of limits.

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