Cue Column:

• What is Mij vs Cij?
• Sign pattern for cofactors?
• How to compute efficiently?

Note Column: The minor $M_{ij}$ is the determinant of the submatrix obtained by deleting row i and column j. The cofactor $C_{ij}$ = (-1)^(i+j) * $M_{ij}$. The sign pattern follows a checkerboard:

+ - +
- + -
+ - +

For a 3x3 matrix, you need 9 cofactors for the adjoint, but each is a 2x2 determinant (quick). Organize systematically:

1. Write out all 9 minors in a grid
2. Apply the sign pattern to get cofactors
3. Transpose to get adjoint

Common error: forgetting to transpose. The adjoint is the transpose of the cofactor matrix, not the cofactor matrix itself.

Summary: Cofactor = signed minor. Sign from (-1)^(i+j). Always transpose cofactor matrix to get adjoint.