# vertical alignment two columns list

I am writing a highschool math textbook and i have a problem with lists. I want to split an itemize in 4 columns. The problem is that, if there math text like franction, I can't make items to be vertically aligned (see the second itemize).

\documentclass[a4paper,12pt]{book}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{multicol}
\newcommand{\parenthesis}[1]{\left( #1 \right)}

\begin{document}

\begin{multicols}{3}
\begin{itemize}
\item[(a)] $2x + 2y = 2(x + y)$
\item[(b)] $x + y = y + x$
\item[(c)] $x + y = 5$
\item[(d)] $x\parenthesis{x^3 + 1} = x^4 + x$
\item[(e)] $2x = -8$
\item[(f)] $3x^2y = -6x^2y$
\end{itemize}
\end{multicols}

\begin{multicols}{4}
\begin{itemize}
\item[(a)] $(x + 5)^2$
\item[(b)] $(y - 4)^2$
\item[(c)] $\parenthesis{3x + 2y^2}^2$
\item[(d)] $\parenthesis{5x^3 - \dfrac{1}{2} \cdot y^2}^2$
\end{itemize}
\end{multicols}

\end{document}


ps. I am sorry for my English.

• Welcome to TeX SX! I suppose you'd like an automatic numbering, but from left to right? – Bernard Jul 25 '16 at 13:54
• It would be great to have automatic numbering from left to right. In fact i want to write code to split a list in columns(2, 3, 4 etc), the items to be vertically aligned and the numbering to be from left to right but it's difficult for me to write it! – alex Jul 25 '16 at 14:05
• Don't try to reinvent the wheel! It already exists: the tasks package. I'll post a solution in a moment. – Bernard Jul 25 '16 at 14:28

Two packages enable to do what you want: shortlst, which is only on CTAN, not in TeX Live not MiKTeX, for copyright reasons, and tasks, a package initially included in exsheets, but which can now be used alone.

I added some improvements to you code: I defined a \parens command, with the DeclarePairedDelimiter command from mathtools. This command manges correctly the spacings around paired delimiters and defines two commands:

• \parens* is equivalent to adding a pair of \left … \right around the parentheses (not recommended, as the spacing is often bad);
• \parens produces a pair of normal parentheses, but also accepts optional arguments for fine-tuning the size of the delimiters: [\big], [\Big], [\bigg] and [\Bigg], equivalent to pairs of \bigl …bigr areound the parentheses.

In addition, I loaded nccmath for its medium math commands and environments (size ~ 80 % of displaystyle), which may be handy sometimes. I used it here for a medium-size fraction.

Here's the demo:

\documentclass[a4paper,12pt]{book}
\usepackage[showframe]{geometry}
\usepackage{mathtools, nccmath}
\usepackage{amsthm}
\usepackage{amssymb}
\usepackage{multicol}
\DeclarePairedDelimiter{\parens}{(}{)}
\newcommand{\parenthesis}[1]{\left( #1 \right)}

\begin{document}

\task $2x + 2y = 2(x + y)$
\task $x + y = y + x$
\task $x + y = 5$
\task $x\parenthesis{x^3 + 1} = x^4 + x$
\task $2x = -8$
\task $3x^2y = -6x^2y$

\task $(x + 5)^2$
\task $(y - 4)^2$
\task  $\parens*{3x + 2y^2}^2$
\task $\parens[\Big]{5x^3 - \dfrac{1}{2} \cdot y^2}^2$
\task*(2) $\smash{\parens*{5x^3 - \dfrac{1}{2} \cdot y^2}^2}$
\task $\parens[\big]{5x^3 - \mfrac{1}{2} \cdot y^2}^2$

• It is not wrong by itself: it's generally better not to use \left … \right` with pairs of delimiters, as it often brings bad horizontal spacing. – Bernard Jul 26 '16 at 15:24