Step 1: Concept
This is a differential equation of the first order but not of the first degree, solvable for $y$.
Step 2: Meaning
Expressing $y$ in terms of $x$ and $p$: $2yp = xp^{2} + ax \Rightarrow 2y = xp + \frac{ax}{p}$.
Step 3: Analysis
Differentiating with respect to $x$ and replacing $dy/dx$ with $p$ allows us to find a relation between $p$ and $x$. Integrating that relation gives $p$ as a function of $x$ and a constant $c$.
Step 4: Conclusion
Substituting the expression for $p$ back into the equation for $y$ simplifies to the general solution: $2y = cx^{2} + \frac{a}{c}$.
Final Answer: (B)