Determinants. All square matrices have a determinant. The only ones we will deal with are 2x2 and 3x3 matrices. To find the determinant of a 2x2 matrix, you use the rule for second order determinants. ad-bc
= a* -b* +c*
First take the first two columns and add them on to the end.
Then draw diagonals from the first entry of each row down and to the right. You obtain aef, bfg, and cdh. Then start at the bottom and draw diagonals up and to the right. You get gec, hfa, and idb.
The determinant will equal aef+bfg+cdh-gec-hfa-idb.
Solve the following:
Solve by expansion by minors:
Solve by diagonals: