1. Chapter 8: Lesson 8.2 Operations With Matrices
2 matrices are said to be equal if the size or “order” of the 2 matrices is the same AND all corresponding elements of the 2 matrices are the same.
2 matrices can only be added if they are of equal order. If you are asked to add or subtract matrices that are not of equal order, simply write “impossible.”
#12 Find A + B, A- B, 3A and 3A – 2B if

2. Definition of Matrix Multiplication
2 matrices can multiplied together only if the number of columns of the 1st matrix is equal to the number of rows of the 2nd matrix. The size or order of the resulting matrix multiplication will be the rows of the first by the columns of the 2nd. In other words, a (3 x 3) (3 x 1) = (3 x 1)
Note that A B ≠ B A (Matrix Multiplication is NOT Commutative)
Be my guest to try and figure out matrix multiplication from page 556, I’d prefer to teach it just through examples and understanding the pattern based on that.

3. #36 Find AB if

4. #35 Find AB if

5. Identity Matrix
An Identity Matrix has all 1’s on the main diagonal and 0’s everywhere else. See page 558.

6. Compute BA and interpret the results
#74 The number of calories burned by individuals of different body weights while performing different types of exercises for a one-hour time period are represented by A.
Calories burned
130-lb
person
155-lb
person
Basketball
Jumping Rope
Weight Lifting
A 130-pound person and a 155-pound person played basketball for 2 hours, jumped rope for 15 minutes, and lifted weights for 30 minutes. Make matrix B that organizes the times spent exercising.
Compute BA and interpret the results