# solve a Lim +- 0

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• November 17th 2009, 10:56 AM
lyovadima
solve a Lim +- 0
Lim +- 0 (1+2^(1/x))/(1-2^(1/x))
• November 17th 2009, 04:21 PM
Drexel28
Quote:

Originally Posted by lyovadima
(1+2^(1/x))/(1-2^(1/x))

Problem: Compute $L=\lim_{x\to0^+}\frac{1+2^{\frac{1}{x}}}{1-2^{\frac{1}{x}}}$

Solution: Let $z=\frac{1}{x}$ which transforms this into $L=\lim_{x\to0^+}\frac{1+2^{\frac{1}{x}}}{1-2^{\frac{1}{x}}}\overbrace{\longmapsto}^{z=\frac{1 }{x}}\lim_{z\to\infty}\frac{1+2^z}{1-2^z}$. Now, with a little manipulation $L=\lim_{z\to\infty}\frac{\frac{1}{2^z}+1}{\frac{1} {2^z}-1}$. Clearly $\frac{1}{2^z}\to0$ so that $L\to -1$.
• November 18th 2009, 05:27 AM
lyovadima
thanks it helps
thanks it helps