Domain = [0,∞)
The given function is
where, y is the price of x in game power boost.
Domain is the set of input values or x-values.
It means the reasonable domain of the given function is the possible number of games. So, domain of the given function can't be negative.
Set builder form of domain is
Interval notation of domain is
Therefore, the reasonable domain for the given function is [0,∞).