If f(x)=ln(x2+y2)f(x) = \ln(x^2 + y^2)f(x)=ln(x2+y2) and yyy is a function of xxx such that y′=x/yy' = x/yy′=x/y, what is the second derivative y′′y''y′′?
(y2−x2)/y3(y^2 - x^2)/y^3(y2−x2)/y3
1/y1/y1/y
000
(x2+y2)/y3(x^2 + y^2)/y^3(x2+y2)/y3