I am having some trouble with these questions, Thank you so much in advance A) Suppose that f (1,2) = . Find a unit vector

I am having some trouble with these questions, Thank you so much in advance

A) Suppose that f (1,2) = <-3,4>. Find a unit vector U such thatDuf(1,2) is maximized, and find the maximum value

B) Find a unit vector U such thatDuf(1,2) = 0

Find the value of for U =<101,103 and f (x,y) =x2sin(y4)+xy