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The formulas are related,just u nid to learn this topic under elementary maths..Change of subject of formula,algebraic equations ..For example under electricity we know that Q=CV and we also know that W=1/2QV..but supposing in a question u are ask to find W(workdone ) and u are not giving Q but u are giving C and V all u need to do is just to substitute for Q and we already know that Q=CV u wil put CV where u see Q so W=1/2QV SO W=1/2(CV)V W =1/2CV^2..You have seen that whole thing change but still d same...and i know that that is one of the typical example of what you are saying...My advice is that you just need to learn and understand those two topics in maths i said above and learn those little formula in physics because it build up to form complex one.