If `u=log sqrt(x^(2) + y^(2))`, then `(del^(2) u)/(del x^(2)) + (del^(2)u)/(del y^(2))` is

If u=log(x^(2)+y^(2)+z^(2)) prove that (del^(2)u)/(del x^(2))+(del^(2)u)/(del y^(2))+(del^(2)u)/(del z^(2) = 2/(x^(2)+y^(2)+z^(2)

If u = log ((x ^(2) y + y ^(2) x)/(xy)) then x (del u)/( del x) + y (del u)/(del y)=

If u =x ^(2) + y ^(2) evaluate (del^(2)f)/(del x ^(2)) + (del ^(2) f)/(dy ^(2)):

If u=(x-y)^(2) , then (del u)/(del x) + (del u)/(del y) is

If u (x,y) = (x ^(2))/( y)- (2y ^(2))/(x) then (del^(2) u)/(del x dely) - (del ^(2) u)/(dely delx) is :

If u (x,y) =x ^(2) + 2xy-y ^(2) then (del u)/(del x) + (delu)/(del y) is:

If u(x,y) =e^(x^(2) + y^(2)) , then (del u)/(del x) is equal to

If u=log (x^(3) + y^(3) +z^(3) - 3xyz) , then (del u)/(del x) + (del u)/(del y) + (del u)/(del z)=