Basically the Heisenberg principle states that particles can be anywhere and it is impossible to determine simultaneously the position and momentum of the particles… so basically you can link this to the idea that electrons occupy clouds because even though they are in orbitals they can be anywhere.

When x=3.. Not sure, because I tried using derivatives and equating the first derivative to 0 and finding x.. Then plug x=3 into the original equation and Y should be 5... (I don't remember parabolas)