Defining that as a function of is equivalent to say "in terms of " Hence, isolate and you'll get a function in terms of What's the name of that curve?
it depends on how the question was phrased.
it might mean you should solve for y and then say whether what you have is a function, or just note that anything that does not look like "y = something with x's in it" is not defined as a function of x. then there might be cases where you can't solve for y altogether, in which those are definitely not the functions you want