How to use greek letter in \systeme

Question

I've been trying to write a simple system that should contain some greek letter. What I tried was this

\documentclass{article}
\usepackage{amsmath}
\usepackage{systeme}
\begin{document}
\[ 
\systeme*{ \lambda + 2\mu = 2, -3\lambda + 3\mu = -1 } 
\]

\[ 
\systeme*{\lambda = 2 - 2\mu} 
\]

\end{document}

But the output I get is this

I can't understand what I'm doing wrong, what I'd like to do is to use both lamba and mu in the equation of the first system and remove the "+" sign before lamba in the second system.

Answer 1

The automatic ordering of terms in systeme only works properly with lower-case latin letters. If you want to use other symbols than a to z, you have to specify those and their ordering as an optional argument:

\documentclass{article}

\usepackage{amsmath}
\usepackage{systeme}

\begin{document}

\[ 
\systeme*[\lambda\mu]{ \lambda + 2\mu = 2, -3\lambda + 3\mu = -1 } 
\]

\[ 
\systeme*[\lambda\mu]{\lambda = 2 - 2\mu} 
\]

\end{document}