Key ideas Minor MijM_{ij}Mij is the determinant formed by deleting row iii and column jjj. Cofactor AijA_{ij}Aij is: Aij=(−1)i+jMijA_{ij}=(-1)^{i+j}M_{ij}Aij=(−1)i+jMij Determinant expansion along a row (e.g. row rrr): ∣A∣=∑j=1narjArj|A|=\sum_{j=1}^{n} a_{rj}A_{rj}∣A∣=j=1∑narjArj