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For each of the following problems, answer whether the given matrix-matrix product is valid or not. If it is valid, give the number of rows and the number of columns of the resulting matrix (you need not provide the matrix itself).

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I don't understand the question, can someone help? Am I missing something here? Shouldn't I calculate the result of these two matrices (making it the product) and then decide whether it's valid or not? I am confused right now.

So my actual question would be: what is the matrix-matrix product in this question? How do I start?

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    The question is asking if it is even possible to multiply them. – 2017-02-19
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    Ah, I thought so, but never knew it was that easy. So I should do the n times m check? Checking if the rows of the first one are equal to the columns in the second one, correct? – 2017-02-19

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Given two matrices, it's not always true that their product is well-defined. In particular, you need the number of rows of the first matrix to equal the number of columns of the second matrix to carry out multiplication. The problem is asking you if the operation is possible here. Since the number of rows of the first matrix doesn't equal the number of columns of the second matrix, the product isn't defined.

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    Fantastic! I was thinking like this as well, but it confused me. Didn't think it was still this easy. Merci! – 2017-02-19