We briefly went through the definitions in Chapter 1. Make sure you
know the definitions.

We finished section 2.4, partitioned matrices. Notice that the
formulas for matrix-matrix products are valid even if we have
"a matrix whose entries are matrices" (which is one way we can
interpret partitioned matrices).

2.4 Exercises 1-4.  When you answer these, remember that matrix
multiplication is not commutative. For instance, if M is the answer
to Exercise 1, then the entry in Row 2, Column 1 should be EA.
It should NOT be AE  because EA and AE need not be equal when A,E are
matrices.

Exercises 5-10: these are good puzzles that will help you to have
a better grip on matrix multiplication.  Again, don't mix up XA and AX,
those are not the same when A,X are matrices.  Later in the book we
will often encounter things like P A P^(-1) and that is usually
not equal to A.

Exercise 15: this may shed some light on the next section.

Turn in Ex 6 and 8.