expressions - "Hope this help" or "Hope this helps"?

Good evening all, I often see people write "hope this helps" at the end of a communication, especially when they are trying to answer other people's queries about computer problems.
Recently, my english teacher pointed out that both "hope this helps" and "hope this help" are grammatically incorrect after she saw a classmate of mine writting the three words in his assignment, but my teacher just didn't explain it in detail why the expressions are wrong.

So, could you tell me why both "hope this helps" and "hope this help" are grammatically incorrect please?

I had asked this question in school. Some of teachers told me that "hope this helps" was perfectly acceptable and they had been using it for many years.

But some told me that "the correct expression should be: Hope this help or I hope this help"

Please help me! Which is correct?
1: hope this helps
2: hope this help
3. I hope this will help. (my suggestion)

Kitty

Answer

So my original answer was incorrect. "Hope this helps!" is a declarative, not an imperative. Instead of deleting my answer, I think it might be helpful to explain why I should have known it wasn't an imperative, and pull out the bits from the original that were correct.

Imperative clauses are usually in the second person, like:
"Hope for the best!" (You should hope for the best.)

A declarative clause is just a statement, like:
"I am editing my answer." or,
"Hope this helps!"

The second person and first person form of hope are the same, so I got a little confused because I didn't think about it carefully. I should have been able to tell that the clause wasn't an imperative because an imperative is usually a command directed at another person, and "Hope this helps!" is stating something in the first person.

I would expand "Hope this helps!" this way:

I hope this (answer) helps you.

You would say "This answer helps me." and not "This answer help me." because the subject of "help" is third person singular. So, "Hope this helps (you)!" is OK, but "Hope this help (you)!" has a verb agreement problem.

In your suggested sentence, which is grammatical, you changed the wish from the present (helps) to the future (will help). This is OK, but it's not exactly what the original author expressed.