# Inverse Matrix of A

I would like to know how to write an inverse matrix off A. I have tried everything i could think off but i had no success. Could anybody give me a simple 2x2 example(I don´t know how to get -1 over the matrix bracket). Thank you

• Here : \begin{bmatrix} 1 & 1 \\ 0 & 1 \\ \end{bmatrix}^{-1} = \begin{bmatrix} 1 & -1 \\ 0 & 1 \\ \end{bmatrix}. – marsupilam Aug 26 '17 at 20:34
• welcome to tex.se! if you will show what you try so far (with small, complete document beginning with \doccumentclass{...} an ending with \end{document} we can help you. otherwise only advice: see en.wikibooks.org/wiki/LaTeX/Mathematics – Zarko Aug 26 '17 at 20:36
• You can put subscripts and superscripts on almost anything in LaTeX maths. You aren't limited to simple cases like $x^2$. – alephzero Aug 26 '17 at 20:42
• I have to do this A^-1=(A b c d)^-1 in matrix form – Igor Krstulović Aug 26 '17 at 20:51
• @IgorKrstulović,than please be so kind and edit your question and show what you have. – Zarko Aug 26 '17 at 20:59

Something like this?

\documentclass{article}
\usepackage{mathtools} % for 'bmatrix*' env.; loads 'amsmath' package automatically
\begin{document}
Let
$A = \begin{bmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{bmatrix}$
be a full-rank $2\times2$ matrix.
Then $\det A\equiv\lvert A\rvert=a_{11}a_{22}-a_{12}a_{21}\ne0$ and
$A^{-1}=\begin{bmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{bmatrix}^{-1} =\frac{1}{\lvert A\rvert} \begin{bmatrix*}[r] a_{22} & -a_{12} \\ -a_{21} & a_{11} \end{bmatrix*} \,.$
\end{document}

• Thank you very much this is exactly what i was hoping for – Igor Krstulović Aug 26 '17 at 21:35