Remove space between bracket and array environment

Question

Sorry for my bad English.

How can I removing space between bracket and array environment and obtained results as used cases environment.

Thank you very much!

I use code

\[\left\{\begin{array}{l} x + y = 1\\ x - y = 2 \end{array}\right.\]
\[\begin{cases} x+y=1 \\ x-y=2\end{cases}.\]

Answer 1

Two options:

One with dedicated aligned environment. And, other by playing with the dedicated \mkern<space>. An example is as follows:

\documentclass[10pt,a4paper]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\begin{document}
\[
    \left\{
    \begin{aligned}
     x + y = 1\\ x - y = 2
    \end{aligned}\right.
\]
    \[\left\{\mkern-10mu\begin{array}{l} x + y = 1\\ x - y = 2 \end{array}\right.\]
\end{document}

which would give you:

Answer 2

Here are two ways:

\documentclass[10pt,a4paper]{article}
\usepackage{mathtools, empheq}
\newtagform{eqt}{(eqt\,}{)}

\begin{document}

\[ \left\{\begin{array}{@{}l} x + y = 1 \\ x - y = 2 \end{array}\right.\]

\begin{empheq}[left=\empheqlbrace]{align*}
   x + y & = 1\\ x - y & = 2
\end{empheq}
\[\begin{cases} x+y=1 \\ x-y=2\end{cases}.\]

\end{document}