Has your homework been finished?
Here's how we transform the sentence:
* Original subject ("you") becomes the object of the preposition "by": This part is usually omitted in passive voice.
* Original object ("homework") becomes the subject: "Your homework" is now the main focus.
* Verb ("have finished") is transformed into passive form ("has been finished"): We use "has" to agree with the new subject "homework" (which is singular).