Please help to solve Question 1 to Question 5

Question | (10%) Let z=""*, where u =cos(xy) and v=x"+y", i OF Find . (a) Fin (b) Find az oy Question 2 (15%) Consider the function F(x,y,z)=x'y3xz' 4yz+y and the point P=(1,R,-1). (a) Find the gradient of the function F at the point P . (b) Find the directional derivative of F' at P in the direction of the vector v=2ij-2k . Question 3 (20%) Let f(xy)=x"+y"+4x4Ry +12. (a) Find the critical point(s) of f(x,y). (b) Use the second derivative test to classify the critical point(s) found in (a). Question 4 (35%) Let f(x,y)=2x"6xy+3Ry+5, on the domain D definedby 0