Consider the function z = f(x,y)-x-xy+y--y. Find the derivative of the function z=f(x,y) at the point 7-i+j (1,-1) in the direction of Find the direction 11 in which the function z = f(x,y) increases most rapidly at the point 1,-1 Find the value of the most rapid increase of z = f(x,y) at the point (1-1) Find the direction 11 in which the function z=f(x,y) decreases most rapidly at the point (1-1)