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So I'm a first time Latex learner and I'm still learning the roots, but I want to do something similar to the example given in the picture.

enter image description here

JPi
  • 13,595
D. Brito
  • 145
  • Which aspects of this screenshot are you trying to reproduce? The curly brace down the left-hand side, the colons, the alignment of the three equations, how to to place material in a subscript position, or something else? Please be specific. – Mico Sep 17 '16 at 22:39
  • Please see also http://tex.stackexchange.com/questions/240868/how-to-write-cases-with-latex and http://tex.stackexchange.com/questions/47170/how-to-write-conditional-equations-with-one-sided-curly-brackets?noredirect=1&lq=1 – Au101 Sep 17 '16 at 22:52
  • @Au101 - As of now, it's not clear which part, or parts, of the screenshot the OP is looking to reproduce. The curly brace is only of several possible style elements... Let's see if the OP responds to my inquiry. If we don't get an answer, the posting can be closed as "unclear what you're asking". – Mico Sep 17 '16 at 22:55
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    @Mico You make a fair point, but the title does say "adding a bracket to a set of equations" ... D. Brito you'd definitely benefit from having a quick read through the links in any case :) – Au101 Sep 17 '16 at 22:57
  • Ok, so I'm trying to add the curly brace down the left together with the equations. I'm sorry for not being clear. – D. Brito Sep 17 '16 at 23:00
  • @D.Brito sure so check out the links, the basic syntax you want is \[ \begin{cases} \ell_{1} : a_{1}x ... \\ \ell_{2} : a_{2}x ... ... \end{cases} \]. Unless of course you have any additional requirements – Au101 Sep 17 '16 at 23:03
  • Alternatively I guess you could use an array \[ \left\{ \begin{array}{l} \ell_{1} : a_{1}x ... ... ... \end{array} \right. \] – Au101 Sep 17 '16 at 23:05
  • Ok, thanks, the cases seemed to do the trick. Although I'll also check out the array. – D. Brito Sep 17 '16 at 23:07
  • I really don't understand why this notation is still around. A brace that is linked to nothing is visually a very bad notation – percusse Sep 17 '16 at 23:36

1 Answers1

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\documentclass{article}

\usepackage{amsmath}

\begin{document}
\begin{equation}
\left\{
\begin{aligned}
 y & = x\\
 z & = a.
\end{aligned} \right.
\end{equation}
\end{document}

* EDIT *

As Werner commented, you can alternatively use the cases or dcases environments; the latter needs the mathtools package. The cases environment is really intended for the end of a line with something else in front. 

\documentclass{article}

\usepackage{mathtools}

\begin{document}
\begin{equation}
\left\{
\begin{aligned}
 y & = x\\
 z & = a.
\end{aligned} \right.
\end{equation}
\begin{equation}
\begin{dcases}
y  = x\\
z  = a.
\end{dcases}
\end{equation}

\end{document}
JPi
  • 13,595
  • cases or dcases seem appropriate here... – Werner Sep 17 '16 at 23:36
  • I don't think cases is right unless there's something to the left of the {, like f(x)=... dcases works, but I've often had the need for the somewhat more flexible and general construct I used in the original example. – JPi Sep 17 '16 at 23:45