- ABC+AB'C+A'BC+A'B'C+A'B'C',
- AC + A'BC + A'B'C + A'B'C',
- C(A+A'B+A'B') + A'B'C',
- C(A + A'(B+B') + A'B'C',
- C ( A + A') + A'B'C',
- C + A'B'C',
but true answer is C+A'B.
Help me, what I missed?
boolean-algebra
but true answer is C+A'B.
Help me, what I missed?
Best Answer
I think that the true answer is $C+A'B'$ and not $C+A'B$ as you suggest.
You did well, but could go on with:
$$C+A'B'C'=(C+A'B')(C+C')=C+A'B'$$
To get hold of the situation you could also make a Venn-diagram on:
$$(A\cap B\cap C)\cup(A\cap B^{\complement}\cap C)\cup(A^{\complement}\cap B\cap C)\cup(A^{\complement}\cap B^{\complement}\cap C)\cup(A^{\complement}\cap B^{\complement}\cap C^{\complement})=$$$$\left[[(A\cap B)\cup(A\cap B^{\complement})\cup(A^{\complement}\cap B)\cup(A^{\complement}\cap B^{\complement})]\cap C\right]\cup[A^{\complement}\cap B^{\complement}\cap C^{\complement}]=$$$$C\cup[A^{\complement}\cap B^{\complement}\cap C^{\complement}]=C\cup(A^{\complement}\cap B^{\complement})$$