Introduction to Matrices

A matrix is a rectangular arrays of numbers, symbols, or expressions, arranged in rows and columns.

There are a number of operations that can be applied to modify matrices, such as matrix addition, subtraction, and scalar multiplication.

When multiplying matrices, the elements of the rows in the first matrix are multiplied with corresponding columns in the second matrix.

The identity matrix $[I]$ is defined so that $[A][I]=[I][A]=[A]$, i.e. it is the matrix version of multiplying a number by one.