Check if 1-x is completely Monotonic function

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I had a question about how can I check whether $f(x)=1-x$ is completely monotonic. Could somebody provide a simple example based on this function.

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According to this, a completely monotonic function must satisty $$ (-1)^n \frac {d^n}{dt^n}f(t)\ge0$$ for all nonnegative $n$ and $t>0$; the special case $n=0$ reduces to requiring $f$ non-negative on $(0,\infty)$. Which your $f$ clearly does not satisfy.

The characterization of completely monotone functions as Laplace transforms of non-negative measures is also a tip-off: if $x=2$, say, you would be representing $-1$ as the integral of a non-negative function.