Hello,
Could you please tell me if we can use 'as well' with negative sentences or not?
Probably it should be "either."
Mary is going to the party. Peter is going, as well.
Mary is not going to the party. Peter is not going either.
Is that what you mean?
If not, could you write a sentence that shows what you mean?
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.