The newest one already has three off-topic close votes. And it is still in the review queue. So let us ignor this one.
702498 is a proof verification. Per the recommendation given here, after the OP received enough feedback on their own attempt, it is reasonable to close it as a duplicate.
So we are left with 80340 and 1111089.
1111089 has more answers, so my choice of the directin of the closeure would be 80340 $\to$ 1111089
If we judge the questions by the context and OP's own effort, then 80340 seems a bit better to me.
What do you think?
(Merging does not seem as a viable solution here, because of different notation: x,y vs. a,b.)
So far I voted to close 702498 (proof verification) as a duplicate.
About the two remaining questions, I will wait a bit whether I will receive some feedback here.
@MartinSleziak More answers, but the 3rd one isn't really helpful (only odd n are treated and in a complex way). Also, both other answers to 1111089 (of "hint:" variety) are covered by the first answer to 80340, which is more thorough. Hence, I voted to close 1111089->80340
The latter is interesting in that the record-breaking traffic did not result in record-breaking volume of questions. The percentage of search visits grew from 88% to 91%.
