Formulae - only numbered formulae required? only, explained, presented, required

luda002

Hi all
Sometimes formulae are presented and explained but there is no number next to them. In some cases, they lead to a formula that has a number assigned to it (eg, equation 4), but other times it doesn’t. In the interests of minimising the rote learning of formulae, am I right in assuming that I don’t need to memorise un-numbered formulae?
Thanks a lot

Makavelim3

Great stuff. Thanks for your post (and other posts too - very useful).