Well I'll write my problem down.

In my discrete maths homework I had to find minimal DNF through Karnaugh map and got: -X1-X2 v -X3X4 v -X1X3-X4 v X1X2X4 ( "-" infront of X means inversion)
Then I needed to find CNF via McCluskey's method which I got: (-X2 v X3 v X4)&(X1 v -X3 v -X4)&(X2 v -X3 v -X4)&(-X1 v X4).
The next task was to transform the CNF from McCluskey method to DNK. After I did that (lots of work opening the brackets) I got:
-X1-X2-X3 v -X1X3-X4 v X1X2X4 v -X1-X2-X4 v -X3X4.
Now I did the prime implicant chart and finished up with this: -X1-X2-X3 v -X1X3-X4 v X1X2X4 v -X3X4.
The task was that the DNF I fould from Karnaugh map and the one I got from making CNF to DNF must be logically equal, but however many times I tried, they werent, and one implicant wasnt needed. They are almost the same, only in the -x1-x2 from karnaugh map the result after implicant chart was -x1-x2-x3 and I have no idea what to do. Done it throught 3 times already and checked for errors. any help?
I made a truth table, and yes 1 of 16 was different. The f(0011) which is 310 and is in the - zone.
Lots of thanks, if someone can help me !