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## Homework Statement

So one question that has me puzzled is writing the following in matrix form:

D

_{β[itex]\nu[/itex]}= A

_{[itex]\mu\nu[/itex]}B

_{[itex]\alpha\mu[/itex]}C

_{[itex]\alpha\beta[/itex]}

The second question, I suppose is similar, and it's writing the following as matrix multiplication:

D

_{αβ}= A

_{α[itex]\mu[/itex]}B

_{[itex]\mu\nu[/itex]}C

_{[itex]\beta\gamma[/itex]}

## The Attempt at a Solution

Alright, so my main confusion comes from the fact that, the way I've been thought is that in order to multiply matrices they need to be the same size. So an (MxN) matrix can only be multiplied with an (RxP) one, if N = R. Now in the first, and in the second one, this is (seems?) not the case, as for example a mu by nu matrix A is multiplied with an alpha by mu matrix B. I suppose that this is not actually the case though, and that I am misunderstanding. My question is, what am I doing wrong here? Could you help me in the right direction? The second equation is giving me same issue really, as I don't know how to represent those matrices in a correct way, as to me they seem to be of the wrong dimensions.

Kind regards