# How to remove the unwanted vertical space?

I'm using Exam class to create solutions, but the flaign* environment does not align my equation with the \part. How do I make them align?

\documentclass[a4paper, twoside, 12pt]{exam}

\usepackage{amssymb,amsmath}
\usepackage{graphicx}
\marksnotpoints
\pointsinrightmargin
\bracketedpoints

\begin{document}
\begin{questions}

\question  The functions $f$ and $g$ are defined by
\begin{align*}
f : x &\mapsto 4-x^2, \ \ x \in \mathbb{R} \\
g : x &\mapsto \frac{1}{x-4}, \ \ x\in \mathbb{R}, \ x \not= 4.
\end{align*}
\begin{parts}
\part[3] Define $f\circ g$ in a similar form.
\end{parts}

\begin{solution}
\begin{parts}
\part
\begin{flalign*}
fg(x) &= f(g(x)) &\\
&=f(\frac{1}{x-4}) \\
&= 4 - \frac{1}{(x-4)^2}
\end{flalign*}
\end{parts}
\end{solution}


Specifically, my problem is here in this image:

This might be a good application for TABstacks, which can be placed inline, unlike align environments.

\documentclass[a4paper, twoside, 12pt]{exam}

\usepackage{amssymb,amsmath}
\usepackage{tabstackengine}
\stackMath
\setstackgap{S}{5pt}% GAP BETWEEN ADJACENT STACKED EQUATION ROWS
\usepackage{graphicx}
\marksnotpoints
\pointsinrightmargin
\bracketedpoints

\begin{document}
\begin{questions}

\question  The functions $f$ and $g$ are defined by
\begin{align*}
f : x &\mapsto 4-x^2, \ \ x \in \mathbb{R} \\
g : x &\mapsto \frac{1}{x-4}, \ \ x\in \mathbb{R}, \ x \not= 4.
\end{align*}
\begin{parts}
\part[3] Define $f\circ g$ in a similar form.
\end{parts}

\begin{solution}
\begin{parts}
\part
\alignShortunderstack{
fg(x) =& f(g(x)) \\
=&f(\dfrac{1}{x-4}) \\
=& 4 - \dfrac{1}{(x-4)^2}
}
\end{parts}
\end{solution}
\end{questions}
\end{document}


If one always wants to process TABstack arguments in \displaystyle, this undocumented code can be added to the preamble

\makeatletter
\renewcommand\TAB@delim[1]{\displaystyle#1}
\makeatother

• @jh4 Great! Glad I could help. Note that the default use of the & tab here =& is opposite the preferred way in amsmath approaches &=. See the tabstackengine docs at ctan.org. There are ways to set the processing mode of & tabs in the package, with macros such as \TABunaryLeft, \TABunaryRight, and \TABbinary. – Steven B. Segletes Jun 2 '15 at 12:32

You have to use inline math here. Maybe like the following:

% arara: pdflatex

\documentclass[a4paper, twoside, 12pt]{exam}
\usepackage{amssymb,mathtools}
\marksnotpoints
\pointsinrightmargin
\bracketedpoints

\begin{document}
\begin{questions}
\question  The functions $f$ and $g$ are defined by
\begin{alignat*}{2}
f : x &\mapsto 4-x^2,  &&\quad x\in \mathbb{R} \\
g : x &\mapsto \frac{1}{x-4}, &&\quad x\in \mathbb{R} \vee x \not= 4.
\end{alignat*}
\begin{parts}
\setcounter{partno}{2} % for demo only
\part[3] Define $f\circ g$ in a similar form.
\end{parts}
\begin{solution}
\begin{parts}
\setcounter{partno}{2} % for demo only
\part
\!\begin{aligned}[t] f(x)\circ g(x) &= f(g(x)) &\\ &= f\Bigl(\frac{1}{x-4}\Bigr) \\ &= 4 - \frac{1}{(x-4)^2} \end{aligned}
\end{parts}
\end{solution}
\end{questions}
\end{document}