Answer Happy

D Question 13 Find the directional derivative of the function at P in the direction of v. f(x,y)-x³-³, P(5.4), - O (922.5) -√2 Ⓒ (-5,252.5) -√2 Ⓒ(1,845.0) -√2 O (5,252.5) √2 O (1,677.5) -√2 Question 14 Find the directional derivative of the function at P in the direction of . f(x,y,z) - xy + y2+xz, P(1,1,1), 7-21+31-9k O 16/√√94 O 28/ √94 O-20/√√94 -8/-√√94 O-28/94

Question 15 Find the unit normal vector to the surface 10x+10y + 5z = 0 at the point (0,0,0). O 101+ 10j + 5k 1 80 Question 16 k Find an equation of the tangent plane to the surface g(xy)-x²-y at the point (7.8.-15). O 14(x-7)+16(y-8) + (z+15) - 0 O 14(x-7)+8(y-8)-(z+15) - 0 O 14(x-7)-16(y-8) + (z+15) - 0 07(x-7)-8(y-8)-(z+15) - 0 O 14(x-7)-16(y-8)-(z+15)=0