http://books.google.com/books?id=qhDFuWbLlgQC&lpg=PP1&pg=PA11#v=onepage&q&f=false"(adsbygoogle = window.adsbygoogle || []).push({});

Until he arrives at eq. 1.5

I don't understand the steps, can anyone explain it?

thanks

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# Invariance of interval in SR

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