26. Find the directional derivative of  F(x,y,z)=xy+2xz-y2+z2 at the point (1, －2, 1) along the curve x =t,y =t−3,z=t2  in the direction of increasing z.
(A)5ee3411359e7f.jpg
(B)5ee3412165d2c.jpg
(C) 11
(D) 13
(E)5ee3412fabb66.jpg

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統計： A(0), B(0), C(2), D(0), E(0) #2348361