### Video Summary:

For any value of n, there is an n × n identity matrix
having 1s down the main diagonal and 0s elsewhere.
The n × n identity matrix is given by
Here, aij = 1 when i = j (the diagonal elements), and
aij = 0 otherwise. Solve the system AX = B, where A is the coefficient matrix, X is the matrix of variables, and B is the matrix of the constants.