I want to ask my friend about interest in engineering a system. How can I ask him?
Do you interest in the system?
Do you interested in the system?
Which phrase is correctly used?
Neither is correct.
You have the verb "to interest" backwards. Here is the structure:
[subject] interests [object]
It is the object of the verb that has the feeling of interest. The object gives attention to the subject. The object feels excited about the subject.
So in your case, it should be:
Does [something] interest you?
Your other form, "interested in", is used in with the passive of the same verb, "to be interested". You could say:
Are you interested in [something]?
And both of these would be correct.
None of your phrases are correct. You may ask
- Are you interested in the system?
- Do you have any interest in the system?