Matrices 2 x 2

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.

What is the determinant of this matrix?

• 5

• -5

• 0

• -12

What is the formula for the determinant of a 2x2 matrix?

• ad-bc

• ab-cd

• ad+bc

• (a+d)(b+c)

What is the determinant of this matrix?

• 0

• 24

• -24

• -12

Find the determinant of the matrix

• 42

• -42

• 22

• -22

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.

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

• 47     30
  9     5

• 17     15
  42     35

• 10     25
  7     1

• not possible because rows do not match columns

What do m, n, p and q equal in this scalar matrix multiplication?

• m=8, n=9, p=-4, q=4 

• m=15, n = -45, p=20, q=-5

• m=20, n=-5, p=15, q=-45

• m=-5, n=20, p=-45, q=15

Subtract

• -5
  -8
  3
  10

• -9
  8
  3
  2

• 5
  -8
  3
  10

• -5
  8
  3
  2