 1 is the multiplicative identify for real #’s : 1· a=a and a· 1 = a  For matrices n X n, the identity matrix has 1’s on its main diagonals and 0’s elsewhere 2 X 2 IDENTITY MATRIX3 X 3 IDENTITY MATRIX

 If A is an n x n matrix and I is the identity matrix, then AI = A and IA = A  2 matrices are Inverse Matrices if the product of the two n X n matrices in both orders is the n X n identity.

AB:BA :

A B Multiply both sides by A -1. Be sure to put A -1 first in order: A -1 · AX = A -1 · B IX = A -1 · B X = A -1 · B

Enter Matrix name, then use x -1 button Try solving the previous problem on your calculator now.