<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">\documentclass[a4paper,12pt]{article}
\begin{document}


{\bf Question}

Write down the differential operator ${\cal L}$ which enables the
following equation to be expressed as ${\cal L}[x(t)] = 0$: $\sin
t \frac{d^2x}{dx^2} + 3t\frac{dx}{dt} + \cos t \, x = 0$

\vspace{.25in}

{\bf Answer}

$${\cal L} = \sin t \frac{d^2}{dx^2} + 3t\frac{d}{dt} + \cos t$$


\end{document}
</pre></body></html>