# What does this (') mean in problem: (A U B)'??

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• Aug 12th 2008, 04:49 PM
NeedHelp18
What does this (') mean in problem: (A U B)'??
whats that apostrophe thing for? help

and here too: A' U B'???

thanks
• Aug 12th 2008, 05:08 PM
skeeter
(A U B)' is the complement of the set A U B ... the set of all elements not in
A U B.

A' U B' is the union of set A's complement and set B's complement.

more info ...

Complement Of A Set (with worked solutions)
• Aug 12th 2008, 05:17 PM
saranya
Quote:

Originally Posted by NeedHelp18
whats that apostrophe thing for? help

and here too: A' U B'???

thanks

hi
it is very simple
i will try to explain u by an example
if Z = the set of numbers from 1,2,3.....10
then A = the set of numbers, that is 2,6,10
and B = the set of numbers, that is 1,3,5,9
A' means the set of numbers which is not in A
then A' = 1,3,4,5,7,8,9
like that B' = 2,4,6,7,8,10
then A' U B' is the set of all numbers in A' and B'
that is A' U B' = the set of numbers that is 1,2,3,4,5,6,7,8,9,10.
now u may understood that apostrophe denotes "not in the set"
ok
• Aug 13th 2008, 01:43 AM
Simplicity
Quote:

Originally Posted by needhelp18
whats that apostrophe thing for? Help

and here too: A' u b'???

Thanks

$P(\text{A}) = P(\text{A})$

$P(\text{A}') = 1 - P(\text{A})$