whether it was... / whether it was not...

[pinkie9]

Someone was checking a document written by his coworker and found something, which looks like a mistake.
He says, to the coworker,

1. Please confirm whether this is a mistake.
2. Please confirm whether this is not a mistake.

Are both grammatically correct?

I think No.2 means he is almost sure it is a mistake and No.2 is close to saying "Isn't this a mistake?"
Am I correct?

Thank you.

[5jj]

S/he is unlikely to ask the coworker to confirm that it is a mistake. S/he might ask the coworker to confirm that (not 'whether') something is not a mistake

[pinkie9]

Thank you so much for your answer.

Maybe my example was not good.
How about other situations, which requires you to use "whether"?
What I'd like to know is if there is difference in meaning between 1 and 2.

1. ... whether (someone/something) is ...
2. ... whether (someone/something) is not ...

[Barb_D]

Using the "not" means you think it's more likely that it's not the case.

In your first example, I think it's probably right. But I may be mistaken and in fact it's wrong. So I ask you to confirm that it's NOT a mistake.

Its not as common I think but it's not wrong.

[pinkie9]

Thank you so much.

Using the "not" means you think it's more likely that it's not the case.

Could anyone show me an example for this please? I can't think of an appropriate context. "whether it is... / whether it is not..." is a question I have always been wondering, but I don't have a particular sentence at hand.

In your first example, I think it's probably right. But I may be mistaken and in fact it's wrong. So I ask you to confirm that it's NOT a mistake.

Its not as common I think but it's not wrong.

I'm having difficulties understanding what these "it" means. Soryy for my poor reading skills.