# Combine alignat and flalign

I have a rather large argument, where I want some equations to have text flushed left. This will usually just be a reference to the problem at hand

My desired outcome is something that looks like the image below. However, I have two specifications

• Align the equation before the arrows
• Flush a), b) and c) to the left.

In my code I did some very ugly manually fitting, to align the equations at the arrows, as I could not figure out how to do it with alignat. Any help would be much appreciated. I tried using alignedat inside flalign however, my compiler did not appreciate that. An MWE to produce the image above is presented below

Note I am not restricted to using either alignedat, alignat or flalign. Any solution that produces an adequate output is very welcome.

# Code

\documentclass[preview,border={0cm 0cm 0cm -0.3cm}]{standalone}
\usepackage{mathtools}
\begin{document}
\begin{alignat*}{3}
a)
&f(x)
= 2 - 3x
&\Rightarrow x
= \frac{2 - f(x)}{3} \hspace{0.25cm}
&\Rightarrow f^{-1}(x)
= \frac{2 - x}{3} \\
b)
&g(x)
= 1 + x^3
&\Rightarrow x
= \sqrt[3]{g(x) - 1}
&\Rightarrow g^{-1}(x)
= \sqrt[3]{x - 1} \\
c)
&h(x)
= \frac{1}{x - 1}
&\Rightarrow x
= \frac{1}{h(x)} + 1 \hspace{0.25cm}
&\Rightarrow h^{-1}(x)
= \frac{1}{x} + 1
\end{alignat*}
\end{document}

\end{document}


What about the following. The equation numbers were achieved using \leqnomode from here (Red lines indicate text width:

\documentclass{article}
\usepackage{mathtools}
\usepackage{amsmath}

\makeatletter
\newcommand{\leqnomode}{\tagsleft@true}
\newcommand{\reqnomode}{\tagsleft@false}
\makeatother

\begin{document}
\leqnomode
\renewcommand\theequation{\alph{equation}}
\begin{alignat}{5}
f(x) &= 2 - 3x
&&\Rightarrow x &&= \frac{2 - f(x)}{3}
&&\Rightarrow f^{-1}(x)
&&= \frac{2 - x}{3} \\
g(x) &= 1 + x^3
&&\Rightarrow x &&= \sqrt[3]{g(x) - 1}
&&\Rightarrow g^{-1}(x)
&&= \sqrt[3]{x - 1} \\
h(x) &= \frac{1}{x - 1}
&&\Rightarrow x &&= \frac{1}{h(x)} + 1
&&\Rightarrow h^{-1}(x)
&&= \frac{1}{x} + 1
\end{alignat}
\reqnomode

\end{document}

• This looks promising, the only problem is that I do not use a), b) in my document, I use \cref to produce the references. What is the difference between using single and double ampersands for alignment? – N3buchadnezzar Sep 12 at 14:19
• @N3buchadnezzar: As fas as I know, All alignat uses pairs of l and r type "columns". To skip an r type column (since you only wanted left alignment), I used && instead of juyt &. – leandriis Sep 12 at 14:34
• @N3buchadnezzar Did you try \tag{\cref{...}}? – egreg Sep 12 at 15:40