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**u**and the values of $D_{u}f $ (-1/2 , 3/2) for which $D_{u}f $ (-1/2 , 3/2) is largest, and is smallest.

How do i go about that? I did it for when $D_{u}f $ (-1/2 , 3/2) = 1 and got $D_{u}f $ (-1/2 , 3/2) = 1 and got

**u**=j and -i. This was after i equated partials for x and y at the point (-1/2, 3/2) and then substituted that into the formula for directional derivative, letting

**u = $u_{1}i + u_{2}j$**

i assume i can do the same to calculate when $D_{u}f $ (-1/2 , 3/2) = 0 and -2, can i? but i am not sure how to work it for when it is largest and smallest.

Any help will be appreciated.