All I can see so far is: $\ln{e^x} = \ln{2x}$ -> $ x = ln{2x} $
How can I solve for x?
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5Are you looking for real $x$ or complex $x$? – S.C.B. Feb 27 '17 at 04:05
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3https://en.wikipedia.org/wiki/Lambert_W_function#Examples – The Chaz 2.0 Feb 27 '17 at 04:06
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1@S.C.B. I do not think this equation has real solutions. Graphing $e^x-2x$ at https://www.desmos.com/calculator/d8oueevfh7 shows that it never crosses the $x$-axis, thus the only roots must be complex. – Michael Wang Feb 27 '17 at 04:10
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@MichaelWang Yes, I proved this in my answer. Thus, why I asked this. – S.C.B. Feb 27 '17 at 04:10
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Note that as we have that $e^a \ge a+1$ for all real $a$, by puting $a=x-1$we have that $$e^{x-1} \ge x$$ For all $x$. Thus, multiplying $e$ on each side gives us that $$e^x \ge ex >2x \implies e^x >2x$$ As $e>2$. Hence, there are no real solutions to $e^x=2x$. However, if you were to include complex solutions, note that our equatio is equvialent to solving $(-x)e^{-x}=-\frac{1}{2}$ $$x=-\mathrm{W}_{n}\left(-\frac{1}{2}\right)$$ Where $\mathrm{W}_{n}$ is the analytic continuation of the product log function.
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@mrnovice I know this inequality from experience. The proof is in the link. – S.C.B. Feb 27 '17 at 05:58
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$$e^x = 2x$$ $$\text {Take ln of both sides}$$ $$\ln(e^x) = \ln(2x)$$ $$x = \ln(2x)$$
These two do not intersect, thus there is no solution.
K Split X
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1I simplified as much and I could, and then showed that there is no real solution, – K Split X Feb 27 '17 at 12:19