How to align equations to the left?

Question

I have this equation on Overleaf that aligns to the right instead of the left. I have followed instructions on other questions found here but it doesn't work.

{\setlength{\abovedisplayskip}{0pt}%
\begin{flalign}
     -\frac{\tau}{2} \sum (x_n - \mu)^2 -b_0\tau -\frac{\lambda_0\tau}{2} (\mu - \mu_0)^2 \\
     = -\frac{\tau}{2}\sum(x_n^2 + \mu^2 - 2x_n\mu) - b_0\tau - \frac{\lambda_0\tau}{2}(\mu^2 + \mu_0^2 - 2\mu\mu_0)\\
     = -\frac{\tau}{2}(\sum x_n^2 + N\mu^2 - 2\mu\sum x_n) - b_0\tau - \frac{\lambda_0\tau}{2}(\mu^2 + \mu_0^2 - 2\mu\mu_0)
\end{flalign}%
}%

How can I align to the left?

Answer 1

i guess that you are looking for the following:

\documentclass{article}
    \usepackage{mathtools}

\begin{document}
\begin{equation}
  \begin{split}
    \MoveEqLeft
-\frac{\tau}{2}\sum (x_n-\mu)^2-b_0\tau
    -\frac{\lambda_0\tau}{2}(\mu-\mu_0)^2 \\
    & = - \frac{\tau}{2}\sum(x_n^2 + \mu^2 - 2x_n\mu) - b_0\tau -
            \frac{\lambda_0\tau}{2}(\mu^2 + \mu_0^2 - 2\mu\mu_0)\\
    & = -\frac{\tau}{2}\Bigl(\sum x_n^2 + N\mu^2 - 2\mu\sum x_n\Bigr) - b_0\tau -
            \frac{\lambda_0\tau}{2}(\mu^2 + \mu_0^2 - 2\mu\mu_0))
  \end{split}
\end{equation}
\end{document}

Answer 2

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{flalign}
 -& \frac{\tau}{2}\sum (x_n-\mu)^2-b_0\tau -\frac{\lambda_0\tau}{2}(\mu-\mu_0)^2 \notag \\
  &= -\frac{\tau}{2}\sum(x_n^2 + \mu^2 - 2x_n\mu) - b_0\tau -
      \frac{\lambda_0\tau}{2}(\mu^2 + \mu_0^2 - 2\mu\mu_0)                                   \\
  &= -\frac{\tau}{2}\Bigl(\sum x_n^2 + N\mu^2 - 2\mu\sum x_n\Bigr) - b_0\tau - 
      \frac{\lambda_0\tau}{2}(\mu^2 + \mu_0^2 - 2\mu\mu_0)) \notag
\end{flalign}

\end{document}