So, I can model growth and decay if I start with assuming that the growth rate is constant:
$\frac{p'(t)}{p(t)}=\alpha$
and then I have
$p'(t)-\alpha p(t)=0$
A general linear differential equation, however, would have the form
$p'(t)-g(t) p(t)=h(t)$
So the growth rate is g(t). What is h(t)?
And what type of thing is this form of equation used to model?
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