solve this

[4 marks The luminosity, L, at a point (x, y, z) in a galaxy is given by 1 L ( x , y , z ) = 1+x2 +92 + 24 i) Find the rate of change of luminosity at (1, -1, 1) in the direction of the vector v = i + j + k. ii) In which direction does L change most rapidly at the point (1, -1, 1), and what is the maximum rate of change of L at (1, -1, 1)