1. L4-5/L4-6
Objective: Students will be able to evaluate determinants of matrices

2. A matrix is a table with rows and columns
A square matrix is a matrix with the same number of columns as rows.
A multiplicative identity matrix gives you a product with 1’s along the main diagonal and 0’s elsewhere.
Multiplicative inverses are written as A and A- 1

4. Show that matrices A and B are multiplicative inverses.
Additional Examples
Show that matrices A and B are multiplicative inverses.
3 –1 –
A = B =

5. Practice (on whiteboards)
Are these multiplicative inverses?

6. Practice (on whiteboards)
Are these multiplicative inverses?

8. Evaluate each determinant.
2 X 2 Matrices, Determinants, and Inverses
LESSON 4-5
Additional Examples
Evaluate each determinant.
–5 –9
a. det
b. det
c. det
4 –3
a –b
b a

9. Practice
Find the determinant

11. Ex 3: Evaluate the determinant of X = .
3 X 3 Matrices, Determinants, and Inverses
8 – –
Ex 3: Evaluate the determinant of X =

12. Ex 4:

13. Practice
Find the determinant

14. 2.

15. 3.

16. 4.
Homework 4.5 P207 #8-12e 4.6 P213 #1-4all