DeMorgan's Theorem Question

Nov 18, 2004 5 Replies

Can (A' B C) + (A B' C) + (A B C') be converted to (A' B C)(A B' C)(A B C') using DeMorgans Theorem. I think not but I have been told that this can be done. If it can be done can anyone explain how to do this. IMO even the truth tables would be different. TIA


No. You are basically saying that AND == OR. (A' B C)+(A B' C)+(A B C') is the equivalent of ((A'BC)'(AB'C)'(ABC')')'

DeMorgan's Theorem says that (AB)' = A' + B', or for three variables (XYZ)' = X'+Y'+Z'

If you substitute: X=(A' B C) Y=(A B' C) Z=(A B C')

Using truth tables:

F1 = (A' B C) + (A B' C) + (A B C') F2' = (A'BC)'(AB'C)'(ABC')'

A B C | X Y Z | F1

-----------+-----------+---- 0 0 0 | 0 0 0 | 0 0 0 1 | 0 0 0 | 0 0 1 0 | 0 0 0 | 0 0 1 1 | 1 0 0 | 1 1 0 0 | 0 0 0 | 0 1 0 1 | 0 1 0 | 1 1 1 0 | 0 0 1 | 1 1 1 1 | 0 0 0 | 0

A B C | X' Y' Z' | F2'| F2

-----------+-----------+----+---- 0 0 0 | 1 1 1 | 1 | 0 0 0 1 | 1 1 1 | 1 | 0 0 1 0 | 1 1 1 | 1 | 0 0 1 1 | 0 1 1 | 0 | 1 1 0 0 | 1 1 1 | 1 | 0 1 0 1 | 1 0 1 | 0 | 1 1 1 0 | 1 1 0 | 0 | 1 1 1 1 | 1 1 1 | 1 | 0

F1 = F2 Q.E.D.

No, inside that expression is A' A = 0. Do you mean (A' + B + C)(A + B' + C)(A + B + C')

Then from that use distributive law of * over + to see what you get.

X+Y+Z = NOT(NOT(X).NOT(Y).NOT(Z))

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