Learn English – the question tag for: “They got the answers, ____

Technically, the part after the comma is a sentence for itself. If you say "question tag" or "tag question" you must refer to the second part of the main sentence, the subordinate sentence.

In this regard the both phrases mean the same.

"He's too weak to walk"

Is he ? suggests that the person asking is doubting, or at least needing confirmation of the assertion.

Isn't he? suggests the person agrees with the assertion.

The point is, they have different meanings and should be used depending entirely upon whether or not the person asking agrees or not with the assertion.