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The missing middle column is $\begin{bmatrix} 0 \\ -16 \\ 9 \end{bmatrix}$. This is obtained by applying the transformation A to the middle column of B, which is $\begin{bmatrix} 0 \\ 2 \\ 3 \end{bmatrix}$.

Conditions: A and B are the specific 3x3 matrices shown in the video.; The method of column-wise composition is used.

Yes, matrix addition is commutative. For any two matrices A and B with the same dimensions, $A + B$ equals $B + A$.

Conditions: Matrices A and B must have identical dimensions.; Entries are real numbers.