Question

Number 13 math help

Answer 1

\[\left| A \right|=\left|\begin{matrix}-4 & 6 \\ 4 & -7\end{matrix}\right|\]
co factors of first row of |A| are -7 and -4
co factors of second row of |A| are -6 & -4
adj A\[=\left[\begin{matrix}-7 & -4 \\ -6 & -4\end{matrix}\right]'=\left[\begin{matrix}-7 & -6\\ -4 & -4\end{matrix}\right]\]
|A|=(-4)(-7)-6(4)=28-24=4
\[A'=\frac{ adj ~A }{ \left| A \right| }=\frac{ 1 }{ 4}\left[\begin{matrix}-7 & -6\\ -4 & -4\end{matrix}\right]\]
\[=\left[\begin{matrix}-7/4 & -3/2 \\ -1 & -1\end{matrix}\right]\]

Answer 2

for 13
cofactors of first row are 0 &-2
cofactors of second row are -5,3
find adj and then complete as above.

Answer 3

Thank you so much!

Answer 4

\[\left| A \right|=\left|\begin{matrix}-4 & 6 \\ 4 & -7\end{matrix}\right|\]
co factors of first row of |A| are -7 and -4
co factors of second row of |A| are -6 & -4
adj A\[=\left[\begin{matrix}-7 & -4 \\ -6 & -4\end{matrix}\right]'=\left[\begin{matrix}-7 & -6\\ -4 & -4\end{matrix}\right]\]
|A|=(-4)(-7)-6(4)=28-24=4
\[A^{-1}=\frac{ adj ~A }{ \left| A \right| }=\frac{ 1 }{ 4}\left[\begin{matrix}-7 & -6\\ -4 & -4\end{matrix}\right]\]
\[=\left[\begin{matrix}-7/4 & -3/2 \\ -1 & -1\end{matrix}\right]\]