Whole xy plane.
Work Step by Step
Since $ f(x,y)=12x-5y $ is a polynomial, then it is defined for all values of $ x $ and $ y $. So the domain of $ f $ is the whole xy-plane.
You can help us out by revising, improving and updating this answer.Update this answer
After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.