Boolean algebra rule?

I am trying to simplify something easy, but it has been a while and ive forgotten some rules:

(a + b) * (~b + c) =? (a * ~b) + (a * c) + (b * ~b) + (b * c) =? [a * (~b + c)] + [b * (~b + c)]

ok so far i have: a(~b+c) + b(~b+c)
there is a rule for this but i cant remember do both the (~b+c) just cancel out like in regular math or what is the rule?

The final answer should be: (a + c)

I know there are other steps that be be taken to simplify differently, however I want to know what to do when your in this situation: a(~b+c) + b(~b+c)

?2011-02-03T08:51:50Z

Favorite Answer

In the previous step, you had:
(a * ~b) + (a * c) + (b * ~b) + (b * c)

At this point, if you wanted, you could just remove the (b * ~b) because that will always be 0. That would leave you with:
(a * ~b) + (a * c) + (b * c)

(I am also pretty sure that you cannot simplify (a + b) * (~b + c) into just (a + c). For example, if a = 0 and c = 1, then the result is 1 if b = 1, but the result is 0 if b = 0. Since the result depends on b, there's no way you can just simplify it away.)