Class CBSE Class 12 Mathematics Differential Equations Q #1505
COMPETENCY BASED
APPLY
3 Marks 2026 AISSCE(Board Exam) SA
Find the general solution of the following differential equation: $x^{2}\frac{dy}{dx}=x^{2}+xy+y^{2}$.

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Detailed Solution

Step 1: Identify the type of Differential Equation

The given equation is $ \frac{dy}{dx} = \frac{x^2 + xy + y^2}{x^2} = 1 + \frac{y}{x} + (\frac{y}{x})^2 $. Since the right-hand side is a homogeneous function of degree 0, this is a homogeneous differential equation.

Step 2: Substitution

Let $ y = vx $. Then, differentiating with respect to $ x $, we get $ \frac{dy}{dx} = v + x\frac{dv}{dx} $. Substituting these into the equation:

$$ v + x\frac{dv}{dx} = 1 + v + v^2 $$

Step 3: Separate Variables

Subtracting $ v $ from both sides, we get $ x\frac{dv}{dx} = 1 + v^2 $. Separating the variables:

$$ \frac{dv}{1 + v^2} = \frac{dx}{x} $$

Step 4: Integration

Integrating both sides:

$$ \int \frac{dv}{1 + v^2} = \int \frac{dx}{x} $$ $$ \tan^{-1}(v) = \ln|x| + C $$

Step 5: Back-substitution

Substitute $ v = \frac{y}{x} $ back into the equation:

$$ \tan^{-1}\left(\frac{y}{x}\right) = \ln|x| + C $$

Final Answer: \tan^{-1}\left(\frac{y}{x}\right) = \ln|x| + C

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student must recognize the homogeneous structure and apply the standard substitution method to transform the equation into a separable form.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the execution of a specific algorithmic sequence: identification, substitution, separation of variables, and integration.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. This aligns with the NCERT curriculum for Differential Equations, testing the student's ability to solve homogeneous equations, a core competency in the Calculus unit.