One of two Greek negatives— οὐ or μή —is found in direct questions to indicate the specific kind of answer the questioner expects. For beginning Greek students, it’s helpful to remember that when translating these Greek questions with negatives into English, your translation should be worded in a way that “puts the expected answer” into your reader’s/hearer’s mind.
(1) When a “Yes” answer is expected to a Greek question, οὐ is used:
οὐ τῷ ὀνόματι ἐπροφητεύσαμεν; (Matt. 7:22).
“Did we not prophesy by Thy name?” (Ans.: “Yes.”)
“We prophesied by Thy name, didn’t we?” (Better—more clearly expecting the “Yes” answer)
(2) Using μή + Indicative mode in direct questions expecting a “No” answer, the questioner would be shaking his head (“No”) from side to side:
εἶπεν οὖν ὁ Ἰησους τοῖς δώδεκα μή καὶ ὑμεῖς θέλετε ὑπάγειν; (John 6:67)
“Then Jesus said to the Twelve, You do not wish to go away also, do you?” (Ans.: “No.”)
A practical, everyday, contemporary way of understanding this is to think about how you would phrase questions in English where you are expecting either a “Yes” or a “No” answer. Put within the realm of parents conversations with their children, it might sound something like this:
Question expecting a “No” answer: “You don’t want Mommy/Daddy to spank you, do you?” (“Nope.”)
Question expecting a “Yes“ answer: “You’d like to go get some ice cream, wouldn’t you?” (“Absolutely yes!”)