How to make the first line of aligned equations sit in the same baseline as the bullet and make the equation left justified?
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{itemize}
\item $3!=3\times2\times1=6$
\item $\tfrac{5!}{3!}=\tfrac{5\times4\times3!}{3!}=5\times4=20$
\item \begin{align*}
\frac{n!}{(n-2)!} &=\frac{n\times(n-1)\times(n-2)!}{(n-2)!}\\
&=n\times(n-1)\\
&=n^2-n
\end{align*}
\end{itemize}
\end{document}