# How can I typeset determinants of Cramer's rule? [closed]

I want to typeset the determinants of the system

$\begin{cases} a_1x+ b_1y = c_1,\\ a_2x+ b_2y = c_2. \end{cases}$


I tried

$D=\left| \begin{matrix} {{a}_{1}} & {{b}_{1}} \\ {{a}_{2}} & {{b}_{2}} \end{matrix} \right| ={{a}_{1}}{{b}_{2}}-{{a}_{2}}{{b}_{1}}$


and

$D_x=\Biggl| \begin{matrix} {{c}_{1}} & {{b}_{1}} \\ {{c}_{2}} & {{b}_{2}} \end{matrix} \Biggr| ={{c}_{1}}{{b}_{2}}-{{c}_{2}}{{b}_{1}}$


I don't understand, I get

• What's wrong with what you have? Please explain exactly what you're after. – Werner Aug 19 '13 at 4:58

I do not see a problem, except that the source can be simplified:

• Many pairs of curly braces can be removed, e.g.: {a} is equivalent to \mathord{a} and a that is already an ordinary atom.
• Package amsmath also provides environment vmatrix.

Example file:

\documentclass{article}
\usepackage{amsmath}

\begin{document}
$D = \begin{vmatrix} a_{1} & b_{1} \\ a_{2} & b_{2} \\ \end{vmatrix} = a_{1} b_{2} - a_{2} b_{1}$
\end{document}


If you are asking for an environment suitable for determinants, there is vmatrix from amsmath package:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$$D_x = \begin{vmatrix} c_{1} & b_{1} \\ c_{2} & b_{2} \end{vmatrix} = c_{1} b_{2} - c_{2} b_{1}$$

\end{document}