Aligning Systems of Equations

I'm trying to line up the variables of systems of equations. The following code:

\left\\{ \begin{aligned} &\alpha + 2&\beta + &\gamma & = 0 \\\\ 3&\alpha + 7&\beta + 5&\gamma & = 1 \end{aligned} \right.

produces the following image: I want the Greek letters and the math symbols to be aligned, with appropriate spacing in between coefficients. I've tried using \begin{aligned} \end{aligned} and \begin{array}{ll} \end{array}{ll} as well, but they also don't provide the desired outcome.

Would anyone be kind enough to help me out? Thank you.

First of all, do not use $$...$$, which is plain TeX, use the LaTeX construct [ ... \].

Second, 4 alignment points require 7 ampersands, not 4: each new column of alignment has to be introduced by an ampersand. So n alignment points require 2n–1 ampersands.

Last: use alignat (or alignedat) to have full control on the spacing between columns of alignment.

Here is a possible code:

\left\{ \begin{alignedat}{4} &\alpha &{} + 2&\beta + {} & &\gamma & & = 0 \\\\ 3&\alpha &{} + 7&\beta + 5 & &\gamma & & = 1 \end{alignedat} However, using the systeme package makes it simpler to type: \[ \systeme[\alpha\beta\gamma]{\alpha + 2\beta +\gamma = 0, 3\alpha + 7\beta + 5\gamma = 1} • I had no idea that \$ was plain TeX, thanks! Unfortunately it seems that for the Github Markdown I'm trying to edit, doesn't seem to work... But \begin{alignedat}{4} \end{alignedat} works perfectly! – Seankala Feb 21 at 15:36 • I've updated with a simpler way to type (the \systeme command from the homonymous package). – Bernard Feb 21 at 15:38 • In your first method, the spacing around the = is not correct. – Steven B. Segletes Feb 21 at 15:42 • \amsldoc (amsmath documentation) and systeme. Feel free to ask any questions. – Bernard Feb 21 at 16:08 • The empty curly braces are there because + (or -) are binary operators with a special spacing w.r.t. the elements on the right and on the left. This can be destroyed by an ampersand, and to compensate, one has to add an empty argument, namely {}. For the number of &, maybe I was not clear enough: each column of alignment, but the first, has to be introduced by an &. Inside this column, the alignment point is specified with another &. Check on my code, you should see this rule is respected. Is this clear? – Bernard Feb 21 at 16:26 Something like this? \documentclass{article} \usepackage{tabstackengine} \begin{document} \[ \left\{ \setstackgap{L}{18pt} \Matrixstack[r]{ \alpha +& 2\beta +& \gamma =& 0 \\ 3\alpha +& 7\beta +& 5\gamma =& 1 } \right.
\end{document} Here's a solution that requires only the basic array package. The following code also sets up a custom array-like environment. \documentclass{article}
\usepackage{array} % for "\newcolumntype" macro
\newcolumntype{C}{>{{}}c<{{}}}
%% set up a little custom enrironment:
\newenvironment{myarray}{%
\setlength\arraycolsep{0pt}
\left\{ \begin{array}{#1}}{%
\end{array} \right.}

\begin{document}
$\begin{myarray}{rCrCrCl} \alpha &+& 2\beta &+& \gamma &=& 0 \\ 3\alpha &+& 7\beta &+& 5\gamma &=& 1 \end{myarray}$
\end{document}