can anyone plz tell me how to get F(vector field) when im given DIV F(div means divergence )
Well, you can always say: Let S be the set of all possible vector fields F such that div F=x+1. In that case, the two examples I just gave you would both be elements in S. But you seem to be asking your question with the assumption that there is a one-to-one correspondence between vector fields and their divergences. This is not the case.