Quote (carteblanche @ Sep 17 2013 10:22pm)

(a+b)' = a'b' is de morgan's theorem. looks like your problem is that you dont really understand what's going on. you need to focus on that before you worry about simplifying imo. look over the laws and practice them with truth tables.

/edit: looks like de morgan's theorem is what you're missing conceptually. you think (abcd)' = a'b'c'd' which is NOT the case. you have to invert everything inside and also switch the operator. conceptually this should make sense.

if any of the things inside is false, then the whole expression (abcd) becomes false. so when you complement it, it becomes true. so to make (abcd)' become true, any of the variables must be false. whereas a'b'c'd' means that everything must be false, as opposed to any. so (abcd)' = a' + b' + c' + d'

keep in mind that when OR'ing terms (or summing them), if any term is true, then the whole expression is true. which is why i like sum of products personally. it's very clear to see what inputs make the whole thing true.