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Adjoint of a matrix

Adjoint

Concept 4 of 10 in Determinants

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Think about this

Take A=[3152]A = \begin{bmatrix} 3 & 1 \\ 5 & 2 \end{bmatrix}. Swap its diagonal entries 33 and 22, and change the signs of the other two. What do you get when you multiply AA by this new matrix?