Solution
= Solution
For independent <geometric random variables> supported on $1,2,\ldots$, put $S=\sum_i x_i$. Multiplication of their <probability mass functions> gives the <likelihood function>
$$
\boxed{\mathcal L(p)=p^n(1-p)^{S-n}},\qquad0<p<1.
$$
There are $n$ terminal successes and $S-n$ preceding failures.