Given inner product ⟨u,v⟩=u1v1+2u2v2\langle u, v \rangle = u_1v_1 + 2u_2v_2⟨u,v⟩=u1v1+2u2v2, what is the norm of u=(1,2)u = (1, 2)u=(1,2)?
3\sqrt{3}3
3
9\sqrt{9}9
9