## Elementary Linear Algebra 7th Edition

$$\left[ \begin {array}{ccc} 1&-1\\ 2&0 \end {array} \right].$$
Let $A$ be a matrix given by $$A =\left[ \begin {array}{ccc} 0&1\\ -2& 1 \end {array} \right].$$ Now, the cofactor matrix of $A$ can be calculated by $$\left[ \begin {array}{ccc} 1&2\\ -1& 0 \end {array} \right]$$ hence the adjoint matrix of $A$ is given by $$\left[ \begin {array}{ccc} 1&-1\\ 2&0 \end {array} \right].$$