Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Using "_" to denote the upper bar, your part is _(_A*_B+A*B).
Now, applying De Morgan two times:
_(_A*_B+A*B) = _(_A*_B)*_(A*B)
_(_A*_B)*_(A*B) = (A+B)*(_A+_B)
now expanding:
(A+B)*(_A+_B) =A*_A+A*_B+_A*B+B*_B
But A*_A = 0 and B*_B = 0, then
(A+B)*(_A+_B) =A*_B+_A*B that is the result written into the book.
I don't see any such Law in the book ... B+!BA = B+A
XY + X'Y' + X'YZ
XY + X'Y' + (X'Y' + X'YZ) - extra parenthesis are mine
XY + X'Y' + X'(Y' +YZ) - this can be reduced like the previous question you had on A + A'B