Differential Equations

The integrating factor for the first-order linear differential equation $\frac{dy}{dx} + \left(\frac{2x}{1 + x^2}\right)y = \frac{1}{(1+x^2)^2}$ is:

Options:

• (A) 1 + x^2
• (B) \ln(1 + x^2)
• (C) \frac{1}{1 + x^2}
• (D) (1 + x^2)^2