Suppose $f \left( x, y \right) = -2 x^{2} + 1 xy - 2 y^{2}$, $P = \left( 2, 3 \right)$, and $\mathbf{u} = \left( \frac{8}{10}, \frac{6}{10} \right)$.

A. Compute the gradient of f.
$\nabla f =$ $\mathbf{i} +$ $\mathbf{j}$
Note: Your answers should be expressions of x and y; e.g. "3x - 4y"

B. Evaluate the gradient at the point P.
$\left( \nabla f \right) \left( 2, 3 \right) =$ $\mathbf{i} +$ $\mathbf{j}$
Note: Your answers should be numbers

C. Compute the directional derivative of f at P in the direction u .
$\left( D_{\mathbf{u}} f \right) \left( P \right) =$
Note: Your answer should be a number