It's actually 2x[1/(x^2 + 1)], you MUST use your brackets correctly, and don't use x to mean both the letter x and times.
Anyway, your function is y = ln(x^2 + 1). If you let u = x^2 + 1 then y = ln(u).
What is du/dx?
What is dy/du?
Once you have those, what is dy/dx?