Answer :
You're given the diagonal decomposition of the matrix:
[tex]\begin{bmatrix}-1&1\\2&1\end{bmatrix}\begin{bmatrix}5&0\\0&-3\end{bmatrix}\begin{bmatrix}-1&1\\2&1\end{bmatrix}^{-1}[/tex]
Computing the product yields
[tex]-\dfrac13\begin{bmatrix}1&8\\16&7\end{bmatrix}[/tex]
[tex]\begin{bmatrix}-1&1\\2&1\end{bmatrix}\begin{bmatrix}5&0\\0&-3\end{bmatrix}\begin{bmatrix}-1&1\\2&1\end{bmatrix}^{-1}[/tex]
Computing the product yields
[tex]-\dfrac13\begin{bmatrix}1&8\\16&7\end{bmatrix}[/tex]