( 1)
A B C Y
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 1
1 0 0 0
1 0 1 0
1 1 0 1
1 1 1 1
(2) Y=ABC+ABC'+A'BC+A'B'C=AB+A'C
(3) Y=((AB)'(A'C)')' 用四个与非门即可