## Describe geometrically the level surfaces of the functions

So the question is as titled

i) f=(x^2 +y^2 +z^2) ^1/2

if I can figure out the method I can solve the other equations but I'm not really sure where to start I know that a function f(x,y,z) of a level surface well be constant so do I just find del f ?
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Here, that gives $(x^2+ y^2+ z^2)^{1/2}= C$. What do you get if you square both sides?