you'd think after all this time i'd remember to blog before 10:00 sunday night...you'd be wrong.

This week I am going to review the oh so exciting concept that is multiplying matrices. Pay attention…this is a toughy.

In order to multiply matrices, the dimensions have to be precise. You must have the same number of columns in the first matrix as rows in the second matrix. If you do not have such dimensions, YOU CANNOT MULTIPLY. If you do not have proper dimensions, the answer is not defined. DO NOT CONFUSE THIS WITH UNDEFINED. Undefined means you have divided by zero. NOT DEFINED means no solution.

-Helpful hint, after multiplying, your answer matrix will have the same number of rows as the first matrix and columns of the second matrix.

Example:
[3 4] [2 3 1] [22 33 23]
[6 7] X [4 6 5] = [40 60 41]
[9 1] [22 33 14]

Since the dimensions of the first matrix are 3x2 and the dimensions of the second matrix are 2x3, your answer matrix will be a 3x3.

First, multiply row one by column one. (I’m going to fill answers into the matrix as I go)
3(2)+4(4)=22

First row second column, then first row third column.
3(3)+4(6)=33 3(1)+4(5)=23

Continue the same process with rows two and three.

That is all.

--Sarah