Find the directional derivative, $f_v$, of the function $f(x, y) = 4 + 2x\sqrt{y}$ at the point $P(2, 1)$ in the direction of the vector $\vec{v} = \langle 3, -4 \rangle$. 1. $f_v = -\frac{2}{5}$ 2. $f_v = -\frac{3}{5}$ 3. $f_v = -\frac{1}{5}$ 4. $f_v = \frac{1}{5}$ 5. $f_v = 0$
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The gradient of a function f(x,y) is given by the vector (∂f/∂x, ∂f/∂y). In this case, f(x,y) = 4 + 2xy, so ∂f/∂x = 2y and ∂f/∂y = 2x. Therefore, the gradient of f(x,y) is (∂f/∂x, ∂f/∂y) = (2y, 2x). Show more…
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