I have a rather simple problem. I have an unwanted indent in my equation.

```
\documentclass[11 pt, a4paper, fleqn]{article}
\usepackage{float}
\usepackage{amssymb}
\usepackage{amsmath}
\setlength{\mathindent}{0cm}
\begin{document}
\noindent Through rigorous analytical calculations found in \textbf{Appendix A} a state space representation was found:

\begin{multline}
X= \begin{pmatrix}\dot{x_1} \\ \dot{x_2} \\ \dot{x_3} \end{pmatrix} =
\begin{pmatrix}0 & 1 & 0\\ 0 & 0 & 1 \\ -1000 & -300 & -30\end{pmatrix}
\begin{pmatrix}x_1 \\ x_2 \\ x_3 \end{pmatrix}+\begin{pmatrix} 0 \\ 0 \\ 160 \end{pmatrix}u \\
\noindent Y=\begin{pmatrix}1 & 0 & 0 \end{pmatrix} \begin{pmatrix}
x_1 \\ x_2 \\ x_3 \end{pmatrix}
\end{multline}
\end{document}

```

Which give me this result:
[enter image description here](https://i.stack.imgur.com/hjvGM.png)

I would like to have the second line at the left margin.
I have tried using `\[ \begin{aligned} \end{aligned} \]` and at the before I begin my document I have the command `\setlength{\mathindent}{0cm}` but still the indent persists. It's driving me quite mad.

Please and thank you!

edit: made compileable