Working with matrices

A matrix is a rectangle of numbers. For example:

The matrix shown previously has two rows and three columns, so we call it a 2×3 matrix (pronounced as two-by-three matrix).

Tip

The plural of matrix is matrices (pronounced as MAY-trih-sees). To sound like a pro, never say matrixes or matricee.

It’s common to use an uppercase to represent a matrix. You refer to the entries in a matrix using the entries’ row numbers and column numbers. Some authors start with row number 1 and column number 1, but, for our purposes, it’s better to start with row number 0 and column number 0.

When you talk about matrices, you need a name that refers to a single number – a number that isn’t inside of a matrix. For example, if you write the number 12 with no parentheses around it, you’re referring to one of these single numbers. A number of this kind is called a scalar.

So, what can you do with...