This is my K-map

AB 00 01 11 10
CD
00 0 1 x 1
01 x 1 0 0
11 x x x 0
10 0 1 1 1

I found f = AD'+A'B
and from the k-map I found f' = AD+A'B'

But from De Morgan's theorem, if I find the complement of f
f' = AD+A'B'+B'D -> I believe this is still correct according to the K-map, but B'D term is redundant, and have no idea how to simplify.

Many thanks

 

The question was find f' for
f(A,B,C,D) = sigma(4,5,6,8,19,14)&don't cares sigma( 1,3,7,12,15)

 

Ah finally got it... sorry and thank you!