Matrix Multiplication Sec. 4.2
Matrix Multiplication #1 3 5 -2 1 4 9 5 2 3 4 X = 3 x 2 2 x 2 Must be equal
Matrix Multiplication #1 3 5 -2 1 4 9 5 2 3 4 __ X = 3 x 2 2 x 2 3 x 2 The resulting matrix size
Matrix Multiplication #2 5 3 -2 4 -1 X 2 1 3 4 5 6 = 3 x 2 2 x 4 Must be equal
Matrix Multiplication #2 5 3 -2 4 -1 __ X 2 1 3 4 5 6 = 3 x 2 2 x 4 3 x 4 The resulting matrix size
Matrix Multiplication #3 2 5 -2 1 4 6 9 Can not multiply these matrices X 2 1 3 4 5 6 2 x 4 3 x 3 not equal
Matrix Multiplication 3 5 -2 1 4 9 5 2 3 4 X Row by Column
Let’s Begin……….
Row 1 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 3 x 5 + 5 x 3 = 30
Row 1 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 3 x 5 + 5 x 3 = 30
Row 1 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 30 = A(1,1)
Row 1 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 3 x 2 + 5 x 4 = 26
Row 1 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 3 x 2 + 5 x 4 = 26
Row 1 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 30 26 = A(1,2)
Row 2 X Column 1 3 5 -2 1 4 9 5 2 3 4 X -2 x 5 + 1 x 3 = -7
Row 2 X Column 1 3 5 -2 1 4 9 5 2 3 4 X -2 x 5 + 1 x 3 = -7
Row 2 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 = A(2,1)
Row 2 X Column 2 3 5 -2 1 4 9 5 2 3 4 X -2 x 2 + 1 x 4 = 0
Row 2 X Column 2 3 5 -2 1 4 9 5 2 3 4 X -2 x 2 + 1 x 4 = 0
Row 2 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 = A(2,2)
Row 3 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 4 x 5 + 9 x 3 = 47
Row 3 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 4 x 5 + 9 x 3 = 47
Row 3 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 47 = A(3,1)
Row 3 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 4 x 2 + 9 x 4 = 44
Row 3 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 4 x 2 + 9 x 4 = 44
Row 3 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 47 44 = A(3,2)
A Quick Review
Row 1 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 30 = A(1,1)
Row 1 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 30 26 = A(1,2)
Row 2 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 = A(2,1)
Row 2 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 = A(2,2)
Row 3 X Column 1 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 47 = A(3,1)
Row 3 X Column 2 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 47 44 = A(3,2)
Matrix Multiplication 3 5 -2 1 4 9 5 2 3 4 X 30 26 -7 47 44 =
One Final Concept with Matrix Multiplication
Matrix Multiplication Not Commutative