This question was put on hold.
That was a most unfortunate decision: the accepted answer makes the unnecessary assumption that the base field is algebraically closed and invokes the absurdly irrelevant Nullstellensatz to solve in a complicated way an easy and purely formal result.
When I wanted to give that easy solution I found out that I couldn't because of the closure of the question (or whatever euphemism is now current).
The negative side of having an unsatisfactory answer accepted and unimprovable far surpasses any worry of "missing context" invoked by the closers.
For what it is worth I am completely uninterested in "context", how much effort the OP put into his question and similar considerations : I am a mathematician and not a moralist (as far as this site is concerned).
I have now answered Voyska's friend's question in a comment, and since I have expressed my point of view on the policies of this site I don't think there is much for me to add to this thread.