Need can be used as a modal verb, but it usually appears in negative form. Must I wash the dishes? Negative answer: No, you need't. Is it right?

Must I wash the dishes? Negative answer: No, you need't. Yes

Can I... Yes, you can. No, you can't

Should I. ． ． ? Yes, you should. No, you shouldn't.

1.He does not need_to　do_______(do) too much homework. Because the auxiliary verb does was used before, need is the substantive verb here, and to do

2.You need to eat more vegetables. (Change to negative sentence)

You don’t need to eat more vegetables.

Because need is not followed by the verb base form, but to is added, so this is a substantive verb