4

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

enter image description here

  • 2
    What's wrong with what you have? Please explain exactly what you're after. – Werner Aug 19 '13 at 4:58
12

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}

Result

| improve this answer | |
5

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} 

enter image description here

| improve this answer | |

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