Float equals sign left in equation

Question

Trying to have an equals sign flush left with the margin, while centring the rest of the equation, found the best solution here, but it seems like there would be a better way to do it, given that the symbol is in the same place every time.

The solution I have:

\begin{align*}
(s + 6.72 + 9.95 j)(s + 6.72 - 9.95 j) \refstepcounter{equation}\tag*{\llap{\makebox[\linewidth][l]{$=$}}}
\end{align*}

Answer 1

Here is an attempt to achieve what you're after, using flalign:

\documentclass{article}

\usepackage{amsmath}

\newcommand{\insertmath}{\rule{5em}{.5\baselineskip}}

\begin{document}

\begin{flalign*}
    && f(x) = \insertmath && \\
  = && (\insertmath)(\insertmath)
\end{flalign*}

\begin{flalign*}
    && & f(x) = \insertmath & \\
  = && & (\insertmath)(\insertmath)
\end{flalign*}

\end{document}