Transcript Do Now: Solve the system graphically.

Do Now: Add or subtract, if possible.
1 5 1  2
 2 0 6  5  8

 

1.)  3
0  0  4 7 
8 1  3  1 2  1

 

2.) 4 1
Academy
Algebra II/Trig
12.4: Matrix
Algebra
HW: p.889 (8, 9,
12, 13, 16, 17, 21)
Scalar Multiplication.
1  2
0  4 7 
Given A  
, B
; find the


5  8 
1 2  1
following:
1.) 3A
2.) -B
Multiplying Matrices
# columns of the first must be the
same as the # rows of the second
matrix.
(r x c)(r x c)
Determine if the matrices can be multiplied.
1 5 1  2
 2 0 6 5  8



1.)  3
0  0  4 7 
8 1  3 1 2  1



2.) 4 1
Operations Using Matrices
2 1  B   3 1 
Find the product AB if A  
 1 2



0 4
Operations Using Matrices
4
2 5 1
2 4  1


A

Find AB if
6
5 8 0  B   4 8 0


 3 1  2  1
Operations Using Matrices
Do Now: Find the product AB if
4


A 1 
 2
B   2 0 1
Academy
Algebra II/Trig
12.4: Matrix
Algebra
HW: p.889 (19,
20, 26 – on calc,
27 – on calc)
Identity Matrix
An identity matrix has the same number of
rows and columns with the 1’s on the main
diagonal and zeros for all other cells.
1 0
0 1 


1 0 0
0 1 0 


0 0 1
Operations Using Matrices
Suppose that
  1 2 0
A

 0 1 3
 3 2


B  4 6
5 2
Find by hand and check your answers
using your calculator.
1.) AI 3
2.) BI 2
Input Matrices on TI-89 Calculator:
1. Press APPS and select Data/Matrix
2. Select 3: New
3. Type– 2: Matrix, Folder– Main, Variable– a
4. Press ENTER, ENTER
5. Input Matrix A.
6. Repeat the steps above for matrix B.
7. Press HOME.
8. On the home screen you can
add/subtract/multiply matrices.
** If you want to rewrite over a current
matrix you can resize it by selecting F6
once you have opened the matrix. **
Input Matrices on TI-83/84 Calculator:
-1
nd
1. Press 2 X to select MATRX
2. Arrow over to EDIT
3. Select a matrix to edit
4. Input the dimensions and # of the Matrix.
5. Repeat the steps above for matrix B.
6. Press 2nd MODE to select QUIT and go
back to home screen.
7. On the home screen you can
add/subtract/multiply matrices: go to
matrix menu and select matrices from the
names menu.