So let's say we wanted this expression right over here only in terms of x. Well, then we could solve, we can figure out what y is in terms of x, and then substitute. So let's do that right over here. If we divide both sides by x, we get y is equal to negative 16 over x. And so let's replace our y in this expression with negative 16 over x. So then we would get our sum of squares as a function of x is going to be equal to x squared plus y squared. Y is negative 16 over x.