The set questions that are clearly stated in the general questions are generally in the fill-in-the-blank questions {x | x >；; 0} This table is a set, and you will definitely be asked to write it as a set. If you want to find the domain of x, you can write it as X >；; 0 X∈(0, +∞) can be written as a set, which is not a big problem. Generally, the first two kinds are written more, because it is more convenient to write. If it is a fill-in-the-blank question, it is not acceptable to ask you to find the solution set of an equation x>, and the latter two forms must be deducted. As for X∈(0, +∞), is there an X∈? It seems that the requirements are not particularly strict. Generally, when writing, the definition of X will be written as (0, +∞). This is what I remember when I was studying. I hope it helps you.