SamverkanLinalgLIU

1.\displaystyle \quad \begin{pmatrix}1&0\\0&{-1}\end{pmatrix}.

2.\quad\displaystyle \frac{1}{2}\begin{pmatrix}1&{-1}\\{-1}&1\end{pmatrix}.

3.\quad \displaystyle \begin{pmatrix}0&{-1}\\{-1}&0\end{pmatrix}

4.\quad\displaystyle \frac{1}{25}\begin{pmatrix}9&{-12}\\{-12}&{16}\end{pmatrix}.