Inverse Matrix/3x3/2/Aufgabe/Lösung

${}{\begin{pmatrix}1&1&0\\7&2&1\\0&0&4\end{pmatrix}}$	${}{\begin{pmatrix}1&0&0\\0&1&0\\0&0&1\end{pmatrix}}$
${}{\begin{pmatrix}1&1&0\\0&-5&1\\0&0&1\end{pmatrix}}$	${}{\begin{pmatrix}1&0&0\\-7&1&0\\0&0&{\frac {1}{4}}\end{pmatrix}}$
${}{\begin{pmatrix}1&1&0\\0&-5&0\\0&0&1\end{pmatrix}}$	${}{\begin{pmatrix}1&0&0\\-7&1&-{\frac {1}{4}}\\0&0&{\frac {1}{4}}\end{pmatrix}}$
${}{\begin{pmatrix}1&1&0\\0&1&0\\0&0&1\end{pmatrix}}$	${}{\begin{pmatrix}1&0&0\\{\frac {7}{5}}&-{\frac {1}{5}}&{\frac {1}{20}}\\0&0&{\frac {1}{4}}\end{pmatrix}}$
${}{\begin{pmatrix}1&0&0\\0&1&0\\0&0&1\end{pmatrix}}$	${}{\begin{pmatrix}-{\frac {2}{5}}&{\frac {1}{5}}&-{\frac {1}{20}}\\{\frac {7}{5}}&-{\frac {1}{5}}&{\frac {1}{20}}\\0&0&{\frac {1}{4}}\end{pmatrix}}$

Zur gelösten Aufgabe