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?