**Problem : **

+ [0] = ? |

**Problem : **

= ? |

**Problem : **
If

= |

what is (

**Problem : **
If
*AI* = *A*
, and
*A*
is a
4×6
matrix, what are the dimensions
of
*I*
?

**Problem : **
If
*IA* = *A*
, and
*A*
is a
4×6
matrix, what are the dimensions
of
*I*
?

**Problem : **
Is there a matrix
*B*
such that
*BB* = *B*
?