Ch. 7 – Matrices and Systems of Equations 7.5 – Operations with Matrices
Matrices What is the order (dimensions) of each matrix? Augmented Matrix: a matrix derived from a system of equations 2 x 13 x 32 x 3 SystemAugmented Matrix (dotted line optional)
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Multiplying Matrices In order to multiply 2 matrices, you must do row-by-column multiplication to calculate entries for the solution matrix. Ex: Find the product of the matrices at right. Multiply the rows of the 1 st matrix by the column in the 2 nd matrix! Since 22 is the product of row 1 of the 1 st matrix and column 1 of the 2 nd matrix, it will go in the 1 st row and 1 st column of the solution matrix Since -14 is the product of row 2 of the 1 st matrix and column 1 of the 2 nd matrix, it will go in the 2 nd row and 1 st column of the solution matrix
Ex: Find the product of the matrices at right. Do row-by-column multiplication!
Ex: Find the product of the matrices at right. Do row-by-column multiplication! Wait…we can’t do this because we can’t multiply a row of 3 entries by a column of 2 entries! Matrix multiplication only works in the following situation: For matrices A, B, and C, other properties of matrices include: A(BC) = (AB)C A(B + C) = AB + AC Equal Order of AB
Ex: Find the product of the matrices at right. It’s a 3x1 times a 1x3…can you do it? The answer will be a 3x3 matrix!
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