# Logic Gates QuestionWatch

#1
Hey,

Been racking my brain at this one for a while now, only been doing AS Computing for a couple of weeks and were currently doing Logic Gates. I need to prove that:

A+Ā.B=A+B (I know some textbooks use different symbols so [+ OR] [Ā NOT A] [. AND])

I really don't see how this could possibly work but according to my computing teacher it does but I dont understand how to get from the A+Ā.B to A+B If anyone could shead any light on this one I would be greatful.

Thanks,
Steve
0
9 years ago
#2
Try using truth tables to prove it if you're allowed to.

I can't think of any basic laws that could simplify that (bit rusty).
9 years ago
#3
(Original post by Sbarkeri)
Hey,

Been racking my brain at this one for a while now, only been doing AS Computing for a couple of weeks and were currently doing Logic Gates. I need to prove that:

A+Ā.B=A+B (I know some textbooks use different symbols so [+ OR] [Ā NOT A] [. AND])

I really don't see how this could possibly work but according to my computing teacher it does but I dont understand how to get from the A+Ā.B to A+B If anyone could shead any light on this one I would be greatful.

Thanks,
Steve
Think of it this way:

If A is true then the result would be true regardless of B.
Else if A is false then the result would be true if and only if B is true.
Since A can only be either true or false then the result is true if and only if either A or B is true.
0
9 years ago
#4
(Original post by K the Failure)
Try using truth tables to prove it if you're allowed to.

I can't think of any basic laws that could simplify that (bit rusty).
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