如果w，x，y，z是布尔变量，那么以下哪一项不正确?
(A) wx + w(x + y)+ x(x + y)= x + wy
(B) (wx’(y + z’))’+ w’x = w’+ x + y’z
(C) (wx’(y + xz’)+ w’x’)y = xy’
(D) (w + y)(wxy + wyz)= wxy + wyz答案： (C)
说明： 1.)
wx + w(x+y) +x(x+y)
= wx + wx + wy + x + xy
= wx + wy + x + xy
= x(w+y+1) + wy
= x+wy
2.)
(wx’(y+z’))’ + w’x
= w’ + w’x + y’z
= w’ + x + y’z
3.)
(wx’(y+xz’)+w’x’)y
= wx’y + wx'xz'+ w’x’y
since x'x = 0
= wx’y + w’x’y
= x’y(w+w')
= x’y thus false
no need to check option 3
这个问题的测验