Ok, I've been working on a matrix solver for a while (no, its not going well, thanks for asking), and just discovered something that worrys me alot;
The problem at hand is LU Decomposition of a square matrix, for example
$\begin{matrix} 1&2&3\\ 2&-1&1\\ 3&4&-1\\ \end{matrix}$
WolframAlpha's answer is completely different from the example source
Wolfram
$\begin{matrix} 1&2&3\\ 3&-2&-10\\ 2&2.5&20\\ \end{matrix}$
Source
$\begin{matrix} 1&2&3\\ 2&-5&-5\\ 3&0.4&-8\\ \end{matrix}$
What's going on?