What is the second partial derivative fyyf_{yy}fyy for f(x,y)=ln(x2+y2)f(x, y) = \ln(x^2 + y^2)f(x,y)=ln(x2+y2)?
2(x2−y2)(x2+y2)2\frac{2(x^2-y^2)}{(x^2+y^2)^2}(x2+y2)22(x2−y2)
2(y2−x2)(x2+y2)2\frac{2(y^2-x^2)}{(x^2+y^2)^2}(x2+y2)22(y2−x2)
2x2(x2+y2)2\frac{2x^2}{(x^2+y^2)^2}(x2+y2)22x2
−2y2(x2+y2)2\frac{-2y^2}{(x^2+y^2)^2}(x2+y2)2−2y2