a) And b) both are same
a) (X +Y) ( X+ Y’ ) ( X’ +Z) = (X+XY’+XY+YY’)( X’ +Z)
= (X+X(Y’+Y)+YY’)( X’ +Z) Since YY’ = 0 and Y+Y’ = 1 Then
= ( X + X(1) + 0 ) )( X’ +Z) Since X + X = X Then
= X ( X’ + Z ) = XX’ +XZ Since XX’ = 0 Then
= XZ
(X +Y) ( X+ Y’ ) ( X’ +Z) = XZ