1. For a given determinant Δ find minors and cofactors of the elements ai2, a3j. Calculate the determinant Δ: a) expanding it to the elements i-th row; b) expanding it to elements of the j-th column; c) obtaining a pre-zeros in the i-th row.
2. Given two matrices A and B. Find: a) AB; b) BA; a) A-1; g) AA-1; d) A-1A

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