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 Post subject: Set algebra questionPosted: Sat, 23 Oct 2010 20:17:08 UTC
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Joined: Tue, 24 Nov 2009 22:30:16 UTC
Posts: 11
Hi, i am a 1st yr software engineering student, so one of our modules in computing mathematics. We are doing sets, i am finding it quite hard as i havnt done maths for a couple of yrs and have only a C at GCSE.

Anyway here is the question :

Prove that : (A n B')' u A = U

(A n B')' u A = (A' u B'') u A Double Complement Law
= (B u A') u A Commutative Law
= B u (A' u A) Associative Law
= B u U Complement Law
= U Domination Law

so thats the answer. I understand it. But in the first line, how does the double complement law make the intersection (n) between A and B' become a union (u) ?

also if anyone could recommend any books, material on this topic so that i can nail algebra sets.

thank you very much

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 Post subject: Re: Set algebra questionPosted: Sat, 23 Oct 2010 21:17:44 UTC
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Joined: Wed, 1 Oct 2003 04:45:43 UTC
Posts: 9961
ukbaz wrote:
how does the double complement law make the intersection (n) between A and B' become a union (u) ?

This is better known as one of De Morgan's laws:

http://en.wikipedia.org/wiki/De_Morgan%27s_laws

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 Post subject: Posted: Sat, 23 Oct 2010 23:49:05 UTC
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Joined: Tue, 24 Nov 2009 22:30:16 UTC
Posts: 11
oh yeh i see now. So he should of wrote Demorgans law instead of Double Complement.

how can i get good at these questions am finding them hard, any advise please

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