Tính tích phân \[\smallint \frac{{2xdx}}{{4 + {x^4}}}\]

\[\frac{1}{4}\arctan \frac{{{x^2}}}{4} + C\]

\[\frac{1}{2}\arctan \frac{{{x^2}}}{2} + C\]

\[\frac{1}{2}\arctan \frac{{{x^2}}}{4} + C\]