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Matrices. Matrices – How to write & What is Order. 2 rows and 3 columns Matrix has order 2x3 (read as “2 by 3”). C T SD. M T W. Matrices. E.g:
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Matrices – How to write & What is Order 2 rows and 3 columns Matrix has order 2x3 (read as “2 by 3”)
C T SD M T W Matrices E.g: A drink stalls sold 160 cups of coffee, 125 cups of tea and 210 glasses of soft drinks on Monday. On Tuesday, it sold 145 cups of coffee, 130 cups of tea and 275 glasses of soft drinks. On Wednesday, it sold 120 cups of tea, 155 cups of coffee and 325 glasses of soft drinks. Design a matrix to represent this information. State the order of your matrix. OR order 3x3
Matrices • Matrix Operations B – A ? Observation 1: Matrices must be same order to add or subtract
Matrices Observation 1: A + B = B + A Addition is commutative Observation 2: (A + B) + C = A + (B + C) Addition is associative
(3 × 2) + (4 × 1) = 10 (3 × 3) + (4 × 1) = 13 (1 × 2) + (2 × 1) = 4 (1 × 2) + (3 × 1) = 5 **Play this slide as slide show to view the multiplication step-by-step Matrices Scalar Multiplication: Remember: ROW multiply by COLUMN Matrix Multiplication:
TV VCD DVD $T $V $D Total for Monday M T Total for Tuesday Matrices An electrical shop sold 5 televisions, 10 VCD players and 15 DVD players on Monday. On Tuesday, it sold 7 televisions, 8 VCD players and 9 DVD players. Given that the price of television is $90, the price of VCD player is $40 and the price of DVD player is $80, find the total sales for Monday and Tuesday.
B A Not possible! (2 x 2) (3 x 2) Not equal! Matrices Can only multiply matrices if these numbers are the same!
AB = BA Multiplication is NOT commutative! Matrices Observation 1: (AB)C = A(BC) Multiplication is associative Observation 2:
Matrices The matrix with all entries zero is called a null matrix. This matrix is called the identity matrix. The diagonal are all 1’s. Observation 1: A0 = 0A = 0 Observation 2: AI = IA = A
Practice • Find • (a) BA • (b) BA – 2A • If , find a and b.
Answer a = − 8, b = 238