Is the indirect question correct?

No.

I disagree with Mark. I don't think the second question is incorrect.

Can you forward me the 'mathematical' formula, as to why?

Both questions are direct.
You have added words to the second question, but that does not make it inderect.
In direct and inderect sentences you change subject to an object and the object to a subject.
What was the first record bought by you?

You're referring to voice.

An indirect question is a question embedded in another, interrogative question.

The second sentence qualifies as an indirect question.

Sorry I was thinking about passiv and active sentences.

It isn't incorrect.

Yes, it is mostly correct, although you need to change the verb order

"Can you remember what the first record was that you bought?"

An indirect question is a politer form than a direct one, and starts with a phrase that signals that an implied question is following: Can you tell me... I was wondering... Do you know... I was wondering if perhaps you might be able to tell me... (extreme example!)

Also the verb/noun order is generally changed compared with a direct question:

What was the first record you bought?
Where is my hat?
What are you doing?

Can you remember what the first record was that you bought?
Can you tell me where my hat is?
Could you tell me what you are doing?

Both are correct.