If `z=ax^(3)+by^(3),`where a and b are arbitrary constants, then `X((del z)/(del x))+y((del z)/(del y))` is equal to:

If u=x^y then find (del u)/(del x) and (del u)/(del y) .

If u=ax-by , then ((del u)/(del y))=

If U=(y)/(z)+(z)/(x), then find x(del u)/(del x)+y(del u)/(del y)+z(del u)/(del z) .

Solve the partial differential equation (del z)/(del y)=xy :

If H=f(y-z,z-x,x-y) Prove that (del H)/(del x)+(del H)/(del y)+(del H)/(del z)=0

If z (x + y) = x ^ (2) + y ^ (2) show that [(del z) / (del x) - (del z) / (del y)] ^ (2) = 4 [1 - (del z) / (del x) - (del z) / (del y)]

If x = r cos theta and y = r sin theta, prove that (del ^ (2) r) / (del x ^ (2)) + (del ^ (2) r) / (del y ^ (2)) = (1) / (r) [((del r) / (del x)) ^ (2) + ((del r) / (del y)) ^ (2)]

If x = r cos theta, y = r sin theta, Find (del (x, y)) / (del (r, theta)), (del (r, theta)) / (del (x, y))