Practice 7.5 Adding and Subtracting Matrices

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

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

Can the operation be performed?

• Yes
• No
• Sometimes
• only Mrs. Jordan knows

What do a, b, c and d equal in this matrix addition?

• a = -1, b = 10, c = 7, d = -11
• a = -1, b = 10, c = -11, d = 7
• a = 10, b = -1, c = 7 , d = -11 
• a = 10, b = -1, c = -11, d = 7