Find a, b, c for question 12

(a) Find the gradient of f. (b) Evaluate the gradient at the point P. (c) Find the rate of change of f at P in the direction of the vector u. 8. f(x, y) = x2ey, P(3, 0), u = 5(31 - 4j) 9. f(x, y) = x/y, P(2, 1), u = itsj 10. f(x, y) = x2 In y, P(3, 1), u = - 5 13 1 + 13 j 11. f (x, y, z) = x2 yz - xyz', P(2, - 1, 1), u = 10, 3, -5 12. f ( x, y, z) = yzexyz z, P(0, 1, -1), u = 3 4 12 13, 13 , 13