Inverse matrix of 2x2 matrix, 3x3 matrix, 4x4 matrix

Inverse matrix of 2 $\times$ 2 matrix There exists an inverse matrix of A when detA=ad-bc 0, and it is Inverse matrix of 3 $\times$ 3 matrix There exists an inverse matrix of A when detA=a 11 a 22 a 33 +a 21 a 32 a 13 +a 31 a 12 a 23-a 11 a 32 a 2

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