Solution
= Solution
Separating variables in
$h'=(h-1)(\lambda h-\mu)$ with $h(0)=0$ gives the <extinction probability of a linear birth-death process>
$$
\boxed{
h(t)=\frac{\mu\left(1-e^{-(\lambda-\mu)t}\right)}
{\lambda-\mu e^{-(\lambda-\mu)t}},
\qquad\lambda\ne\mu.}
$$
For $\lambda>\mu$ this tends to $\mu/\lambda$; for $\lambda<\mu$ it tends to one, as expected.