is y=g(x) a function?
If a rule produces a single output for any given input, then the rule represents a function.
Usually, the rule is denoted f, the input is represented by the variable x, and the output produced by the rule f, is y, such that:
f(x) = y
The problem provides the equation g(x) = y, hence, in this case, the rule that produces the output y, for any given input x, is the rule g, such that g(x) = y.
Hence, the given relation `g(x) = y` represents a function.