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boolean-logicboolean-expressionboolean-algebra

Boolean algebra 2 different simplification?


Wondering why the following boolean expression seem to have 2 possible simplification? Are these two both correct ? Thank you very much !

How online tutorial solves it: enter image description here

How I simplify it

enter image description here

How online tool sovles it <--- Same as my answer enter image description here


Solution

  • When you use a Karnaugh map you will see that they are the same. See the following Karnaugh map for this boolean expression, almost completely matched with circles:

    KV map partially filled

    The blue circle matches the expression BC, the red circle matches the expression B'C'. The remaining cell at AB'C still needs a circle. There are three ways to create a circle, which matches this cell:

    KV map completely filled solution 1.)

    In this solution, the cell AB'C is matched by a circle with only one cell. However this is not the biggest circle possible in this Karnaugh map. The circles chosen in a Karnaugh map are picked to be the biggest circle possible (according to the Karnaugh map rules).

    The "real" other solutions are:

    KV map completely with left circle

    The green circle in this solution matches AC. The remaining third solution is this one:

    KV map completely with right circle

    The green circle in this solution matches AB'.

    This means that all these three boolean expressions are equal:

    • BC + B'C' + AB'C (can still be more simplified, shows what happens when too small circles are choose in Karnaugh maps)
    • BC + B'C' + AC (your solution)
    • BC + B'C' + AB' (solution from the video)