Question 15(3 points)

Consider functionf(x,y,z) =x²y

{"version":"1.1","math":"$-$"}2y²z+xz²

{"version":"1.1","math":"$-$"}13x.At point(2,

{"version":"1.1","math":"$-$"}1, 1), depending on the direction given by a vectorv, the directional derivativef_v(2,

{"version":"1.1","math":"$-$"}1, 1) has different values.The largest value off_v(2,

{"version":"1.1","math":"$-$"}1, 1) is

Question 15 options:

a)

9

b)

21

c)

15

d)

18

e)

11

f)

7

Question 15 (3 points) Consider function f (x, y, z) = xzy 2y22 + x22 13x . At point (2, 1, 1), depending on the direction given by a vector v, the directional derivative fv (2, l, 1) has different values. The largest value of fv (2, l, 1) is