Boolean Algebra question (doubt is inside)

[Deleted]

Hello, if you understand what Boolean Algebra is , then this thread should be for you! I'm in serious need of help here , there is some exercise from an old exam, which asks to simplify an expression via Boolean Algebra.

I got the solution with me (it was solved by the teacher) , but there is a part in the end that completely annoys me because I REALLY can't figure out what the hell he has done there.
This is the problem:

http://imgur.com/C46RmTH

Does anyone have any idea how he went from C(D AB + AB ) into C(D + AB) ? (the very first AB, close to D is negated as you see on the image)

[Linkedblade]

Been thinking about this perhaps D and not (A and B) becomes D and (not A or not B) . perhaps that use DeMorgan's eliminates that term. Not studied Boolean algebra so this is new to me.

[Ealyssa]

It's just a simplification.

like :

A + ÅB = A + B

(Å being non-A, don't know if their is a ascii code for the right symbol)
Nearly 10 years old, but pretty sure it's that.

[Deleted]

It's just a simplification.

like :

A + ÅB = A + B

(Å being non-A, don't know if their is a ascii code for the right symbol)
Nearly 10 years old, but pretty sure it's that.

It is indeed buddy, just figured it out , thanks for the help! Holy jesus it was right there and I couldn't see it.

[Sloshi]

I don't think it's using DeMorgan's Law, however in Boolean Algebra there's some tricks that can help simplify the problem or rearrange the equation. You can prove these by drawing up truth table, but with practice they'll come naturally!

I can't attach an image that will detail other tricks like these because I'm new to these forums, but for your question: B.NOT(A) + A == B + A (which is a simplified version of your problem).
Hope that helps!
If you want the image I can email it to you

link to image:
tinypic.com/r/2hgg09t/5