Suppose that f(x,y)=x3y2\displaystyle {f{{\left({x},{y}\right)}}}={x}^{{3}}{y}^{{2}}. The directional derivative of f(x,y)\displaystyle {f{{\left({x},{y}\right)}}} in the directional ⟨−1,−2⟩\displaystyle {\left\langle-{1},-{2}\right\rangle} and at the point (x,y)=(3,−3)\displaystyle {\left({x},{y}\right)}={\left({3},-{3}\right)} is   .

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