not actually sure what you are trying to do (my math skills are bad!!) but it looks like r2 = x2 + y2. you are trying to assign the result of your equation (y2+x2) to a function Math.pow(r,2), which doesn't make sense since Math.pow is returning a value. You can only pass it a value inside the (). also y is never defined and you are trying to send it to your outlet.
The below should work and give you r2 (y is a constant right now).
I'm sure someone with more js and math chops will explain it better, but maybe this will get you started.