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For which $d$ values does the equation $$x - d\tanh(x) = 0$$ have a positive solution?

I have tried rearranging this a number of different ways using the exponential form and and using hyperbolic trig identities but I am not entirely sure what I am looking for exactly.

Am I trying to find a positive solution for $x=d\tanh(x)$? How am I supposed to relate $d$ and $x$?

EDIT: I have a provided answer of $d = \frac{1}{\operatorname{sech}^2(x)} > 1$.

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