# flalign doesn't work in for me

I want to left justify my equations using flalign. However,it works in some places and doesn't in others. Below is a sample of my code

\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
%%%%%%No Hypernation%%%%%
\tolerance=1
\emergencystretch=\maxdimen
\hyphenpenalty=10000
%%%%%%%%%%%%%%%%%%

\title{Homework 3}
\begin{document}
\newcommand{\pd}{\dfrac{d #1}{d #2}}
\begin{enumerate}

\item Write an ODE file to return the following derivatives
\begin{flalign*}
\pd{n}{t} &= \left( 1-n \right) \alpha_n\left( V\right)-n\beta_n\left(V\right)\\
\pd{m}{t} &= \left( 1-m \right) \alpha_m\left( V\right)-m\beta_m\left(V\right)\\
\pd{h}{t} &= \left( 1-h \right) \alpha_h\left( V\right)-h\beta_h\left(V\right)\\
\pd{V}{t} &=-\dfrac{1}{C}\left(G_kn^4\left(V-E_k\right)+G_{Na}m^3h\left(V-E_{Na}\right)+G_L\left(V-E_L\right)\right)
\end{flalign*}
and the following constants ( $C$ is membrane capacitance, $G$ are the conductances and
$E$ are the reversal potentials of the potassium ( $K$ ), sodium ( $Na$ ), and leak ( $L$ )
channels):
\begin{flalign*}
\alpha\\
C &=1\\
G_K  &= 36\\
G_{Na} &= 120\\
G_L &= 0.3\\
E_K  &= -72\\
E_{Na} &= 55\\
E_L &= -49.4
\end{flalign*}
\end{enumerate}
\end{document}

• Side note: Upright d symbols for differentials look better
– user31729
Jul 4 '15 at 14:25
• Don't use flalign. Use align instead and the fleqn option for amsmath, as in \usepackage[fleqn]{amsmath}. Jul 4 '15 at 14:29
• the fl in the fleqn option stands for flush left, the fl in flalign stands for full length, not flush left. Don't blame me, I didn't think of the names:-) Jul 4 '15 at 15:48
• @ChristianHupfer I disagree: it looks worse. It's basically a stylistic decision, when the document is about pure mathematics. In some technical fields you're required to use an upright “d”, but that's a different story. Jul 4 '15 at 17:22
• @egreg: I disagree to your opinion. In Physics/Science upright d are preferred.
– user31729
Jul 4 '15 at 19:13

The alignment should be used with, well align or align* and left align with fleqn option of the amsmath package.

In my point of view the constant block should use two (or even three constants) per row, not one large column.

And I've changed the differentials d to use upright characters.

\documentclass[12pt]{article}
\usepackage[fleqn]{amsmath}
\usepackage{amsfonts}
%%%%%%No Hypernation%%%%%
\tolerance=1
\emergencystretch=\maxdimen
\hyphenpenalty=10000
%%%%%%%%%%%%%%%%%%

\newcommand{\mathup}{\mathrm{#1}}%

\title{Homework 3}
\begin{document}
\newcommand{\pd}{\dfrac{\mathup{d} #1}{\mathup{d} #2}}
\begin{enumerate}

\item Write an ODE file to return the following derivatives
\begin{align*}
\pd{n}{t} &= \left( 1-n \right) \alpha_n\left( V\right)-n\beta_n\left(V\right)\\
\pd{m}{t} &= \left( 1-m \right) \alpha_m\left( V\right)-m\beta_m\left(V\right)\\
\pd{h}{t} &= \left( 1-h \right) \alpha_h\left( V\right)-h\beta_h\left(V\right)\\
\pd{V}{t} &=-\dfrac{1}{C}\left(G_kn^4\left(V-E_k\right)+G_{Na}m^3h\left(V-E_{Na}\right)+G_L\left(V-E_L\right)\right)
\end{align*}
and the following constants ( $C$ is membrane capacitance, $G$ are the conductances and
$E$ are the reversal potentials of the potassium ( $K$ ), sodium ( $Na$ ), and leak ( $L$ )
channels):

\begin{align*}
\alpha & & C           &=1\\
G_K  &= 36 & G_{Na}  &= 120\\
G_L &= 0.3 & E_K  &= -72\\
E_{Na} &= 55 & E_L &= -49.4
\end{align*}

% All in a column %

\begin{align*}
\alpha\\
C &=1\\
G_K  &= 36\\
G_{Na} &= 120\\
G_L &= 0.3\\
E_K  &= -72\\
E_{Na} &= 55\\
E_L &= -49.4
\end{align*}

\end{enumerate}
\end{document} • There are so many wrong \left\right pairs! :-( Jul 4 '15 at 17:22
• @egreg: Yes, but it's not my job to correct anything, in my point of view
– user31729
Jul 4 '15 at 19:12

Use

\documentclass[12pt,fleqn]{article}