Find the gradient of f(x,y)=12x2y2f(x,y) = \frac{1}{2}x^2 y^2f(x,y)=21x2y2 at the point (2,−1)(2, -1)(2,−1).
⟨2,−4⟩\langle 2, -4 \rangle⟨2,−4⟩
⟨2,4⟩\langle 2, 4 \rangle⟨2,4⟩
⟨4,−2⟩\langle 4, -2 \rangle⟨4,−2⟩
⟨−2,4⟩\langle -2, 4 \rangle⟨−2,4⟩