In the following LaTeX document, which uses the aligned environment inside multlined, there is an superfluous space after the opening { compared to when multlined is replaced by split:
\documentclass[a4paper]{article}\usepackage{mathtools}\begin{document}\begin{gather}\begin{multlined}%\begin{split}\begin{rcases}a_1\\a_2\end{rcases} = \\\left\{\begin{aligned}b_1\\b_2\end{aligned}\right\}x%\end{split}\end{multlined}\end{gather}\end{document}How can I remove the superfluous space?I have seen similar questions, e.g. aligned in multlined produces superfluous space, but they are different, because there, the superfluous space is before the closing } instead.
Example with multlined:
Example with split: