Quick question on Sets

[duragezic]

Wow, this sucks. I take notes of everything, I have two different Discrete books (the actual required one for the class is COMPLETELY useless, this 2yr old different author book is 10x more useful), as well as notes from the web, but I can't find ANY examples dealing with these,.


So I'm stuck on the very 1st problem of like 100, so if anyone could clear something up I could probably do the rest of this garbage.

A = {a,b}
B = {b,c,{a,b},{a,c}}
C = {{empty], {a,b,c}, {a,b}, {a, c}, {a,a }}
D = empty
E = { { empty } }
U = { A or B or C or D or E }

Our answers must NOT have duplicate elements, so for instance part c) A or B

I would respond with A or B = {a,b,c,{a,b},{a,c}}, but does this include duplicate elements? I can't see wtf {a,b} is suppose to mean when a,b is already in there. And like why would E have double bracket for the empty yet D is just empty?

Another question is that for say, find A' (complement), then I know that's U-A from my notes, but I don't get if thats simply U = { B or C or D or E } or if its writing them all out, in which case I don't see how the set inside of a set work. Wtf is {a,a} anyway??

 

[duragezic]

Anyone?

Just tell me if these are right:

A'? U = {c, {a,b}, {a,c}, {empty}, {a,b,c}, {a,a}, empty }

(C and B)' = { a,b,c,{empty},{a,b,c}, {a,a} empty }


I dont wanna get too far into it and have all these set-inside-of a set crap wrong, cause remember there are to be no duplicates in the set, and I don't know if {a,a} is equal to {a} or just a or what.

 

[duragezic]

I think I'm doing something wrong. I keep getting empty sets.

For instance

(A and C ) and A: I get empty set

(C and D) and A: I get empty set

I'm prolly misunderstanding the set inside of a set stuff..