Adding, Subtracting and Multiplying Matrices

How many rows are in a 7 x 3 matrix?

• 7
• 3
• 21
• 10

Find A+B

• 8     10
  8      1 
• 12     25
  7     1
• 10     30
  0     1
• can't add two together because the rows dont match columns

How many columns are in a 5 x 4 matrix?

• 5
• 4
• 20
• 9

Find B-A

• -4     0
  6     -1
• 1     0
  1     -4
• 4       0
  -6     1
• not possible because rows do not match columns

Add

• 11    8
  -4     2
• 3     2
  -6    -6
• -3    2
  -4    -6
• 10    8
  -6    2

Find A+B

• 8     10
  8      1 
• 12     25
  7     1
• 10     30
  0     1
• can't add two together because the rows dont match columns

What must be true in order to ADD two matrices?

• They must be square.
• The dimensions must be equal.
• The determinant can't equal 0.
• The column of the 1st must equal the row of the 2nd.

Subtract

• -5
  -8
  3
  10
• -9
  8
  3
  2
• 5
  -8
  3
  10
• -5
  8
  3
  2

Subtract

• 3    -8
  0   -1
• 3   -4
  8  -13
• -3   8
  0    1
• 3   -8
  -8    1

2 X 2 = 

• 100
• 200
• 4
• 80