Find all points x where f achieves a local maximum or minimum for the

following functions (i.e. all the turning points). State whether f has local

maximum or local minimum at each point.

F(x) = (x^2 + 1) / (x^2 - 1)

I have got f'(x) = -4x / (x^2-1)^2

and then what should I do..? I also got f''(x) is {-4(x^2-1) + 16x^2(x^2-1)} / (x^2-1)^4

..But I don't know what I can do for next..

Please help me