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Sec 4.2. Multiplying Matrices. In order to multiply matrices. A • B = AB. m x n. m x p. n x p. equal. Ex 1. Can you multiply? What will the dimensions be?. AB. A. B. 2 x 3. 3 x 4. 2 x 4. AB. A. B. 5 x 3. 5 x 2. Not possible. How to multiply.
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Sec 4.2 Multiplying Matrices
In order to multiply matrices... A • B = AB m xn m x p nx p equal Ex 1 Can you multiply? What will the dimensions be? AB A B 2 x 3 3 x 4 2 x 4 AB A B 5 x 3 5 x 2 Not possible
How to multiply... Multiply the individual element in each row of the first matrix by the corresponding element in eachcolumn of the second matrix!! ac ad = bc bd 2 x 1 1 x 2 2 x 2
Ex. 2 If there is more than 1 element in the row/column, add the products together FindAB -12 + 2 -15 -10 -16 + 1 = 0 - 4 -2 - 4 0 - 2
Ex. 3 FindBA
Ex. 4 -1(4) +5(6) -1(-3) +5(8) -4 + 30 3 + 40 20 +12 -15 + 16 5(4) +2(6) 5(-3) +2(8) = 0 + -24 0 + -32 0(4) + -4(6) 0(-3) +-4(8) 26 43 32 1 -24 -32