Actually, that has a very simple answer. The inverse function to is, by definition, , "Lambert's W function". It cannot be written in terms of elementary functions.
See http://en.wikipedia.org/wiki/Lambert's_W_function
Actually, that has a very simple answer. The inverse function to is, by definition, , "Lambert's W function". It cannot be written in terms of elementary functions.
See http://en.wikipedia.org/wiki/Lambert's_W_function