ENTER THE MATRICES
Chp 4 USING MATRICES
JAMAAL C.
ALG 2
Section 3- The section deals with the multiplying of matrices.
First you must notice that you can multiply two matrices only if the number of columns in the first matrix is equal to the number of rows in the second matrix. Which will give you the row and column for your answer matrix.
Ex. 2 x 2 2 x 3 = possible 2 x 3 2 x 2 = not possible Row= across Column= up and down [2 3] [7 6 2] [1 3 4] [1 2]
[6 7] [9 4 0] [4 6 1] [7 8]
Now when multiplying the matrix you must multiply row by column. Rows are going across and the columns are going down. Lets try an example.
[2 -1] [3 -9 -2] & First step is to see if this problem is possible. A 2x2 and 2x3 is possible.
[3 4] [5 7 -6] & Your answer matrix is going to be a 2x3. Now take the first row's 2 times the first column's 3 then -1 times 5 and add them together. You should get 1 which you will place in the first row, first column in your answer matrix. Now take first's rows 2 times second column's -9 then -1 times 7. Now take the first row's 2 times -2 and -1 times -6. Your first row should look like this [1 -25 2]. Follow these procedures to get your second row. The final answer should be [1 -25 2]
[29 1 -30]
Try these Practice Problems to see if you understand.
1) [6 4] [2] 2) [5 -1] [4] 3) [9 7] [6 5]
[3] [4 3] [7] [8 4] [-2 3]
Answers:
1) [24] 2) [13] 3) [40 66]
[ 5 ] [40 52]
KINDNESS- THOSE WHO ARE KIND TO OTHERS ARE THE ONES WHO LATER ON IN LIFE RECEIVE THEMSELVES AN OUT STRETCHED HAND.
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