There are two concepts being tested in this question. 1: Your ability to identify the domain of a piece-wise function and 2: Your ability to express this domain in interval notation. You had a responsibility to make it clear what it was that you do not understand about the problem. You failed in this obligation. If you want our help, repost this with a proper explanation of what it is about the question that requires our help.
John
My calculator said it, I believe it, that settles it