x(dy)/(del x)-y=2x^(3)

x (dy)/(dx) - y = 2x ^(3)

If f(x,y) =2x^(3) - 11x^(2)y + 3y^(3) , prove that x(del f)/(del x) + y(del f)/(del y)=3f .

If u is a homogenous function of x and y of degree n, then x(del^(2)u)/(del x^(2)) + y(del^(2)u)/(del x del y) = __________ (del u)/(del x) .

If u(x,y) = (x^(2) + y^(2))/sqrt(x+y) , prove that x(del u)/(del x) + y(del u)/(del y) = 3/2 u .

If u= tan^(-1) ((x^(3) + y^(3))/(x-y)) , Prove that x(del u)/(del x) + y(del u)/(del y) = sin 2u .

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

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

If u=f(y/x) , then x(del u)/(del x) + y(del u)/(del y) =_________

If v(x,y) = log((x^(2) +y^(2))/(x+y)) , prove that x(del v)/(del x) + y(del v)/(del y)=1 .

If y=f(x+ct)+g(x-ct), then show that (del^(2)y)/(del t^(2))=c^(2)(del^(2)y)/(del x^(2))