i think i'm starting to see the light at the end of the tunnel (and the funny thing is i used to know these things but now it's all muddled up).
i'd say "the equation x=a+b" but "equation (1)" etc.
i wish i'd find some serious guidelines somewhere. i've poked around scribd and some academic papers there and those i've perused say "the equation x=a+b". things are easier when there's a prepositional object.
thanks TGS! i'll follow your advice