Need help understanding precalc symbols?

Studying for precalc. Came across this weird symbol I have never seen before. Ā If A = {3, 6, 9, 12} would this mean A ≠ {3, 6, 9, 12} and that would be the acceptable answer? This is just the way I am looking at it but it seems to be wrong. Another symbol I am looking at is this... show more Studying for precalc. Came across this weird symbol I have never seen before.

Ā

If A = {3, 6, 9, 12}
would this mean A ≠ {3, 6, 9, 12} and that would be the acceptable answer? This is just the way I am looking at it but it seems to be wrong.


Another symbol I am looking at is this one:
http://i.imgur.com/iidxQBR.png

Again I have never seen this symbol but I know it will be on a quiz soon.
2 answers 2