Issues with Systeme

Question

\documentclass[12pt]{article}

\usepackage{systeme}
\usepackage{amsmath}

\begin{document}
...

\[
\systeme*{(x+y)\sqrt{xy}=504,x^2+6xy+y^2=2016}
\]

...
\end{document}

I'm getting a compiler error and the message is in French... The error seems to occur after I type "6xy" or just "xy" after the "6."

Anyone know what's wrong?

Welcome to TeX.SX! I'm afraid that systeme only supports linear systems. — egreg, Mar 27 '16 at 00:21
Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. — Martin Schröder, Mar 27 '16 at 00:26

score 2 · Answer 1 · answered Mar 27 '16 at 08:28

@egreg is right, it only works for linear system.

The error you get is described in the documentation (footnote 2 page 1 of http://mirror.ibcp.fr/pub/CTAN/macros/generic/systeme/systeme_doc_fr.pdf) It means that system's algorithm find two instance of the same unknown (in that case x) in one equation. Thus the algorithm cannot align correctly your terms.

To do it, i suggest you to use another environment:

\documentclass[12pt]{article}
\usepackage{systeme}
\usepackage{amsmath}

\begin{document}
\[
\left\{\begin{aligned}
    (x+y)\sqrt{xy} &= 504  \\ 
    x^2+6xy+y^2 &= 2016
\end{aligned}\right.
\]
\end{document}

I wouldn't even try aligning the equals sign, but that's a question of personal taste. — egreg, Mar 27 '16 at 08:42

score 0 · Answer 2 · answered Feb 24 '20 at 16:54

The package is for linear systems only. But using it's substitute command you can fake that:

\documentclass{standalone}
\usepackage{systeme}
\begin{document}
  \syssubstitute{{a_1}{x^2}{a_2}{xy}{a_3}{y^2}}  
  \sysdelim..
  \systeme{a_1 + 2 a_2 + a_3 = (x + y)^2,
           a_1 - 2 a_2 + a_3 = (x - y)^2,
           a_1         - a_3 = (x - y) (x + y)
  }
\end{document}

Issues with Systeme

2 Answers2

Linked