Find the second order partial derivative fxyf_{xy}fxy for f(x,y)=ln(x2+y2)f(x, y) = \ln(x^2 + y^2)f(x,y)=ln(x2+y2).
−4xy(x2+y2)2\frac{-4xy}{(x^2 + y^2)^2}(x2+y2)2−4xy
2(x2+y2)2\frac{2}{(x^2 + y^2)^2}(x2+y2)22
−2xyx2+y2\frac{-2xy}{x^2 + y^2}x2+y2−2xy
4xy(x2+y2)2\frac{4xy}{(x^2 + y^2)^2}(x2+y2)24xy