Flushleft align text in in align environment

Question

I wanted to flushleft align the text in my align environment. Basically, I wanted to get this effect:

Here is my code:

\documentclass{article}
\usepackage{amsmath,amsfonts,amssymb,amsthm, bm}

\begin{document}

\begin{flalign}
\mbox{For the \emph{steady-state filter system}}  \quad\quad  \bm{\Phi}_{f} & = (\mathbf{I}-\mathbf{\bar{K}h'})\bm{\Phi}&\\
\mbox{For the \emph{steady-state predictor system}}  \quad\quad  \bm{\Phi}_{p} & = (\mathbf{I}-\mathbf{\bar{K}h'})\bm{\Phi}&
\end{flalign}

\end{document}

Answer 1

You're forgetting some &:

\documentclass{article}
\usepackage{showframe}% just for the example
\usepackage{amsmath,amsfonts,amssymb,amsthm, bm}

\begin{document}

\begin{flalign}
&\text{For the \emph{steady-state filter system}}    &
  \bm{\Phi}_{f} & = (\mathbf{I}-\bar{\mathbf{K}}\mathbf{h}')\bm{\Phi} &&\\
&\text{For the \emph{steady-state predictor system}} &
  \bm{\Phi}_{p} & = (\mathbf{I}-\bar{\mathbf{K}}\mathbf{h}')\bm{\Phi} &&
\end{flalign}


\end{document}

I fixed the syntax: \mathbf{\bar{K}h'} is conceptually wrong. Even if it's longer, use logical markup:

\bar{\mathbf{K}} \mathbf{h}'

is the correct input.