Step 4: Now, find the second derivative f''(x) by differentiating f'(x). Use the quotient rule: if g(x) = (2x) and h(x) = (x^2 + 1), then f''(x) = (g'h - gh')/h^2.
Step 5: Calculate g' = 2 and h' = 2x.
Step 6: Substitute into the quotient rule: f''(x) = (2(x^2 + 1) - (2x)(2x))/((x^2 + 1)^2).
