Find the directional derivative of f(x, y, z) = y at P(6, 1, -5) in the direction from P to Q (5, 2, -4). NOTE: Enter the exact answer. Duf =Find the directional derivative of f at P in the direction of a. f (x, y) = 3x y; P(3, 5); a = 31 - 4j Duff =Find the directional derivative of f at the point P in the direction of a. f(x, y) = 923 - 8y'; P(4,0); a=i-j NOTE: Enter the exact answer. Duf =