Bob

]]>I know the rule for multiplying two matrices. I dareay you could devise a rule for three but it would be hard to remember. So two at a time is simplest.

You shouldn't assume that matrices can be swopped around like numbers but associativity { (AB)C = A(BC) } does work.

Beware: commutativity doesn't. { AB ≠ BA }

Did you try my practice suggestion?

and you should find that inverse A = E3.E2.E1

This would be a good check that you have inv A right and that your multiplying is OK.

Bob

]]>Always break a big problem down into smaller pieces that you know how to do. This top down design is very common in programming. You knew how to do 2 matrices.

]]>This would be a good check that you have inv A right and that your multiplying is OK.

Bob

]]>Your inverses are correct, so then you need to do the multiplying.

(AB)C = A(BC) for matrices so you have a choice of which pair you multiply first. But you must preserve order.

eg if AB = D you then do DC not CD.

I'm going to do these both ways in case I choose the way you didn't (if you see what mean)

or

Bob

]]>Your mistake is in line 3. Check how you multiplied those matrices.

]]>Thanks a lot]]>

I am getting:

which can be inverted.

]]>Thanks in advance]]>