Adding, Subtracting and Multiplying Matrices

Find the values of w, x, y and z.

• w = 13, x = 4, y = 7, z = 23

• w = 13, x = -4, y = 11, z = 23

• w = 13, x = 4, y = 11, z = 23

• w = 13, x = 4, y = 11, z = 17

Which sums can NOT be made from the following matrices ?

• A+A

• A+C

• B+D

• C+C

• 
• 
• 
• 

• 2

• 7

• 4

• -3

If A is a 2 × 3 matrix, and B is a 3 × 4 matrix, how many columns does AB have?

• 2

• 3

• 4

• AB is not defined

Matrices can be multiplied only...

• if the row of the first matrix is equal to the column of the second matrix.

• if the column of the first matrix is equal to the column of the second matrix.

• if the column of the first matrix is equal to the row of the second matrix.

• if the row of the first matrix is equal to the row of the second matrix.

The matrix A - B is

• 
• 
• 
• 

find: B*A

• 47     30
  9     5

• 17     15
  42     35

• 10     25
  7     1

• not possible because rows do not match columns

What is matrix addition?

• Multiplying the corresponding elements of two matrices together.

• Subtracting the corresponding elements of two matrices.

• Dividing the corresponding elements of two matrices.

• Adding the corresponding elements of two matrices together.

What is matrix multiplication?

• Multiplying the corresponding elements of two matrices together.

• Subtracting the corresponding elements of two matrices.

• Dividing the corresponding elements of two matrices.

• Multiplying the rows of the first matrix with the columns of the second matrix.