# I can't run this code

    \documentclass{article}
\usepackage{unicode-math}
\setmathfont{XITS Math}

\begin{document}
The quadratic formula is
\\\\
$x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}$
\end{document}


I am running this program using Xelatex but it gives the error in line 3. !undefined control sequence and !Latex error Missing \begin{document}

• What TeX distribution are you using? By the way, you should never use \\ in order to “leave a blank line”, and \\\\ will always end up in an error (No line to end). – egreg Nov 21 '14 at 10:35
• You will have to load \usepackage{mathtools} or amsmath in front of unicode-math (or get rid of the dfrac) – LaRiFaRi Nov 21 '14 at 10:36

## 1 Answer

\dfrac is defined in amsmath but never use \\ to force line breaks:

  \documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{XITS Math}

\begin{document}
The quadratic formula is
$x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}$
\end{document}

• The OP says the error is at line 3, which makes me suspect \setmathfont is the problem; the processing didn't get past \begin{document}. – egreg Nov 21 '14 at 10:48
• Now it is giving the same error on line 4 If i remove \usepackage{unicode-math} and \setmathfont{XITS Math} it works fine. – Shaheryar Nov 30 '14 at 16:22
• @Shaheryar the above document worked without error for me, if it fails for you put the entire log in your question in a {} code block. – David Carlisle Nov 30 '14 at 16:27