$l, m, n$ are the $p^{\text {th }}, q^{\text {th }}$ and $r^{\text {th }}$ term of a G.P. all positive, then…
$l, m, n$ are the $p^{\text {th }}, q^{\text {th }}$ and $r^{\text {th }}$ term of a G.P. all positive, then $\left|\begin{array}{ccc}\log l & p & 1 \\ \log m & q & 1 \\ \log n & r & 1\end{array}\right|$ equals