Step 1: Concept
We use substitution by manipulating the integrand. Multiplying both the numerator and the denominator by $x^3$ allows us to substitute $u = x^4$.
Step 2: Meaning
We can rewrite the integrand as:
\[ I = \int \frac{x^3}{x^4(x^4 + 1)} \, dx \]
Step 3: Analysis
Let:
\[ u = x^4 \implies du = 4x^3 \, dx \implies x^3 \, dx = \frac{du}{4} \]
Substitute this into the integral:
\[ I = \frac{1}{4} \int \frac{du}{u(u + 1)} \]
Using partial fractions:
\[ I = \frac{1}{4} \int \left(\frac{1}{u} - \frac{1}{u+1}\right) \, du \]
\[ I = \frac{1}{4} \left( \ln|u| - \ln|u+1| \right) + C = \frac{1}{4} \ln \left| \frac{u}{u+1} \right| + C \]
Substituting $u = x^4$ back into the expression:
\[ I = \frac{1}{4} \ln \left| \frac{x^4}{x^4 + 1} \right| + C \]
Step 4: Conclusion
The value of the indefinite integral is $\frac{1}{4} \ln \left| \frac{x^4}{x^4 + 1} \right| + C$.
Final Answer: (A)