10-17 Adding matrices

Homework for 10-17 - Page 51 and 52; items Try these a, b, c, 8a, 9b, 9c

Scalar multiplication means multiplying number by a matrix.

4S, when S is the 3x3 matrix on page 49, means multiply each entry of S by 4.
This is similar to distributing the 4 over all the entries inside the grouping symbols, although this time it's brackets and not parentheses.

You can add or subtract matrices only if the dimensions are the same.

You can add a 2x2 to a 2x2.  You can add a 3x2 to a 3x2.

You CANNOT add a 2x3 to a 3x2.  You CANNOT add a 1x4 to a 2x3.

To add or subtract matrices, add or subtract corresponding entries. An entry is a corresponding entry if it has the same row and column position in its matrix as another entry has in its matrix.

A matrix is a simpler representation of a table of information.
The rows of a matrix have information about the labels on the left.  Rows run left to right.
The columns of a matrix have information about the labels on top.  Columns run up and down.