But there are no solutions for y!!! The book says that
x=6 and y=1
How?!
The matrix $\displaystyle \begin{bmatrix}-2&x\\ y&-1 \end{bmatrix}$ is what is wrong. It should be $\displaystyle \begin{bmatrix}\color{red}-5&x\\ y&-1 \end{bmatrix}$.
The matrix $\displaystyle \begin{bmatrix}-2&x\\ y&-1 \end{bmatrix}$ is what is wrong. It should be $\displaystyle \begin{bmatrix}\color{red}-5&x\\ y&-1 \end{bmatrix}$.