Hello. I'm going through Ray D'Inverno's "Introducing Einstein's Relativity" and I'm stuck at a certain point and can't move forward. It deals with tensors, I'm stuck at the transformation matrix and the problem is, I can't figure out what the key equation (5.7) actually means. There is a screenshot of the part of the page below, and I have no idea even how to start understanding it. What is it? What was it derived from? How do you actually use it? The left-hand side looks like a(adsbygoogle = window.adsbygoogle || []).push({}); 1x1matrix and the right-hand side looks like an x nmatrix and, of course, that wouldn't make any sense. If someone could write a few helpful sentencesorpoint me in the direction of an Idiot's Guide to Tensor Differentiation, I would be most grateful. Thank you.

Screenshot:

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# Stuck with tensors, need a push

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