You've already seen glimpses of matrices -- determinants (for Cramer's Rule) and Gaussian elimination...  Now, we'll see what else we can do with them.

A matrix is just a rectangular grid of numbers.  Keanu Reeves will tell you otherwise, but don't believe him.

Here are some examples:

[ row 1: 1 , 3 , 0  row 2: -2 , 6 , 4 ][ row 1: 13  row 2: 2  row 3: -4 ][ row 1: 0 , -3  row 2: 2 , 10 ]

"Matrices" is the plural of "matrix."

We'll need some terminology...

[ row 1: 1 , 3 , 0  row 2: -2 , 6 , 4 ] ... each number is an entry

 

These are
the rows

[ row 1: 1 , 3 , 0  row 2: -2 , 6 , 4 ]row 1


row 2

 

These are the columns

[ column 1: 1 , -2  column 2: 3 , 6  column 3: 0 , 4 ]