# Alignment of equation using \begin{align}

When I use the begin{align*} the equation starts in the red part. How can I start it in the blue part?

\documentclass[a4paper]{article}
\usepackage[margin=1.5cm]{geometry}
\usepackage{amsmath}
\usepackage{xcolor}

\begin{document}
Tex\\
My text
\begin{align*}
\color{red}x^2+2x
\end{align*}
\begin{align*}
\hspace{-9cm}\color{blue}x^2+2x
\end{align*}
My text
\end{document}

• Do I interpret your question correctly as not wanting to center a displayed equation? If that's correct, do you want to left-align all displayed equations? Please advise.
– Mico
Sep 19 at 22:43

The answer provided by @MarcelKrüger shows you how to go about having all displayed equation left-aligned. If what you need to achieve is to left-align just this particular pair of equations, I suggest you employ an flalign* environment, as follows:

\documentclass{article}
\usepackage[a4paper,margin=1.5cm]{geometry}
\usepackage{amsmath}
\usepackage{xcolor}

\begin{document}
Text\\
My text
\begin{flalign*} % <-- observe: 'flalign*', not 'align*'
&\color{red} x^2+2x  & \\
&\color{blue}x^2+2x  &
\end{flalign*}
My text
\end{document}


You can request amsmath to align equations on the left by setting the fleqn (flush left equations) option: Replace \usepackage{amsmath} with \usepackage[fleqn]{amsmath}.

This will still indent the equations by a fixed amount which can be changed by setting \mathindent. You could set this to zero to move the equations completely to the left, but I would recommend against this to make the equations easier to differentiate from regular text.

\documentclass[a4paper]{article}
\usepackage[margin=1.5cm]{geometry}
\usepackage[fleqn]{amsmath}
\usepackage{xcolor}
% \setlength{\mathindent}{0pt} % Uncomment this line to get equations completely aligned on the left.

\begin{document}
Text\\
My text
\begin{align*}
&\color{red}  x^2+2x \\
&\color{blue} x^2+2x
\end{align*}
My text
\end{document}

• +1. I've taken the liberty of editing your code to employ a single two-line rather than two consecutiy one-line align* environments.
– Mico
Sep 19 at 22:54

By use of the nccmath you can some align math environments locally align at left border by inserting it in fleqn environment:

\documentclass{article}
\usepackage{geometry}
\usepackage{nccmath}
\usepackage{xcolor}

\usepackage{lipsum}

\begin{document}
\lipsum[66]
{\color{red}
\begin{align*}
y & = x^2+2x    \\
z & = 2y
\end{align*}
}
\lipsum[1][1-3]
\begin{fleqn}\color{blue}
\begin{align*}
y & = x^2+2x    \\
z & = 2y
\end{align*}
\lipsum[1][4-5]
\begin{align*}
y & = x^2+2x    \\
z & = 2y
\end{align*}
\end{fleqn}
\lipsum[1][5-6]
{\color{red}
\begin{align*}
y & = x^2+2x    \\
z & = 2y
\end{align*}
}
\lipsum[66]
\end{document}