If u=⟨1,2⟩\mathbf{u} = \langle 1, 2 \rangleu=⟨1,2⟩, what is u⊥\mathbf{u}^\perpu⊥ (a vector perpendicular to u\mathbf{u}u in R2\mathbb{R}^2R2)?
⟨2,1⟩\langle 2, 1 \rangle⟨2,1⟩
⟨−2,1⟩\langle -2, 1 \rangle⟨−2,1⟩
⟨−1,−2⟩\langle -1, -2 \rangle⟨−1,−2⟩
⟨1,−2⟩\langle 1, -2 \rangle⟨1,−2⟩