Question

Find adjoint of each of the matrices. \(\begin{bmatrix}1&2\\3&4\end{bmatrix}\)

Answer 1

Let A=\(\begin{bmatrix}1&2\\3&4\end{bmatrix}\)

we have A₁₁=4, A₁₂=-3, A₂₁=-2, A₂₂=1

so adj A=\(\begin{bmatrix}A_{11}&A_{12}\\A_{21}&A_{22}\end{bmatrix}\)

=\(\begin{bmatrix}4&-2\\-3&1\end{bmatrix}\)