# Problem with “alignedat” block: minus not correctly spaced

I have an "issue" with the following code:

\documentclass[border=1pt]{standalone}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}
\begin{document}
\begin{math}
\Leftrightarrow \left\{
\begin{alignedat}{1}
&c = -4a + 2b + 3 \\
&-3a + 3b + 3 = 6 \\
&4b + 3 = 15
\end{alignedat}
\right.
\end{math}
\end{document}


Which produces:

As we can see, the minus of the second line is not correctly aligned (too much forward).

Now check the following code:

\documentclass[border=1pt]{standalone}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}
\begin{document}
\begin{math}
\Leftrightarrow \left\{
\begin{alignedat}{2}
&&c = -4a + 2b + 3 \\
&&-3a + 3b + 3 = 6 \\
&&4b + 3 = 15
\end{alignedat}
\right.
\end{math}
\end{document}


Which produces:

We can see that the minus of the second line is now correctly aligned, but the third line completly gone away... We can also note that the minus is closer to the "3a".

My question is: how I can do to get both minus aligned and third line correctly in its place? Like in the following image (which is a photomontage):

Thanks for help and regards.

• Your 2nd alignment is normal: you indicated two alignment columns, but specified only one alignment point, so by default the alignment of the second column is at the end of lines. – Bernard Mar 17 '19 at 16:31

You shouldn't use \{ or $ for such things. amsmath already give you cases environment: \documentclass{article} \usepackage{amsmath} \begin{document} \[\Leftrightarrow\begin{cases} c = -4a + 2b + 3 \\ -3a + 3b + 3 = 6 \\ 4b + 3 = 15 \end{cases}$

• Thanks for your reply, can you explain me the usefulness of the $, $ in the present case? – MissingBracket Mar 17 '19 at 16:31
• @MissingBracket They are LaTeX (not TeX) commands for display-style math-mode. You can change them to \$ (it becomes in-line math-mode), or \begin{math} and \end{math} without any problems. – user156344 Mar 17 '19 at 16:33