What is the gradient of f(x,y,z)=x+y+zf(x, y, z) = x+y+zf(x,y,z)=x+y+z?
⟨1,1,1⟩\langle 1, 1, 1 \rangle⟨1,1,1⟩
⟨0,0,0⟩\langle 0, 0, 0 \rangle⟨0,0,0⟩
⟨x,y,z⟩\langle x, y, z \rangle⟨x,y,z⟩
⟨1,0,0⟩\langle 1, 0, 0 \rangle⟨1,0,0⟩