$139$

$\left(\begin{matrix}-4&9&4\\9&-9&2\\-4&5&-3\end{matrix}\right)$

$\left(\begin{matrix}\frac{17}{139}&\frac{47}{139}&\frac{54}{139}\\\frac{19}{139}&\frac{28}{139}&\frac{44}{139}\\\frac{9}{139}&-\frac{16}{139}&-\frac{45}{139}\end{matrix}\right)$

$-16$

$\left(\begin{matrix}-4&9&-4\\9&-9&5\\4&2&-3\end{matrix}\right)$

$3,3$

$\left(\begin{matrix}1&0&0\\0&1&0\\0&0&1\end{matrix}\right)$

$\left[\begin{array}{rrr}17 & 47 & 54 \\ 19 & 28 & 44 \\ 9 & -16 & -45\end{array}\right]$