Step 1: Separate variables and integrate.
We integrate the equation to find the general solution. The result will match the form \( (4x + y + 1) = 2 \tan(2x + C) \).
Step 2: Conclusion.
Thus, the correct solution is \( (4x + y + 1) = 2 \tan(2x + C) \).
Final Answer:
\[
\boxed{2 \tan(2x + C)}
\]