Second derivatives!?

Question

f = ln(x^2 + y^2 + z^2) find fxy, fyx and fzx! I've found fx = 2x/(x^2 + y^2 + z^2); fy = 2y/(x^2 + y^2 + z^2) and fz = 2z/(x^2 + y^2 + z^2)

Answer 1

not particular sure when you mean fxy, fyx, fzx... are the first derivative or 2nd ?? and you want to see the 2nd derivative of what? please give extra details for it.

Answer 2

The second derivative of f with respect to x and y is

- 4 x y / (x^2 + y^2 + z^2)^2

The second derivative of f with respect to any two of those variables is the same thing, just replace the x and y in the numerator with those two variables.