As far as I know, Y(X) cannot be expressed in elementary functions in general.

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## Re: help for my son

so the equation can be written as or . Let Z= -Yln(X). Then and so the equation becomes and then .

Now apply "Lambert's W function" to both sides. "Lambert's W function" is**defined**as the inverse function to so . Of course, "Lambert's W function" is NOT an "elementary function" so emakarov is completely correct.