Class CBSE Class 12 Mathematics Differential Equations Q #1822
COMPETENCY BASED
APPLY
5 Marks 2026 AISSCE(Board Exam) LA
Find the general solution of the differential equation $(x^{3}-3xy^{2})dx=(y^{3}-3x^{2}y)dy$.

AI Tutor Explanation

Powered by Gemini

Detailed Solution

Step 1: Rearrange the equation

The given equation is $(x^{3}-3xy^{2})dx=(y^{3}-3x^{2}y)dy$. We can write this as: $$\frac{dy}{dx} = \frac{x^{3}-3xy^{2}}{y^{3}-3x^{2}y}$$ This is a homogeneous differential equation of degree 3.

Step 2: Substitution

Let $y = vx$, then $\frac{dy}{dx} = v + x\frac{dv}{dx}$. Substituting these into the equation: $$v + x\frac{dv}{dx} = \frac{x^{3}-3x(vx)^{2}}{(vx)^{3}-3x^{2}(vx)} = \frac{x^{3}(1-3v^{2})}{x^{3}(v^{3}-3v)} = \frac{1-3v^{2}}{v^{3}-3v}$$

Step 3: Separate variables

Subtract $v$ from both sides: $$x\frac{dv}{dx} = \frac{1-3v^{2}}{v^{3}-3v} - v = \frac{1-3v^{2}-v^{4}+3v^{2}}{v^{3}-3v} = \frac{1-v^{4}}{v^{3}-3v}$$ Rearranging for integration: $$\int \frac{v^{3}-3v}{1-v^{4}} dv = \int \frac{1}{x} dx$$

Step 4: Integration

Split the integral: $$\int \frac{v^{3}}{1-v^{4}} dv - 3\int \frac{v}{1-v^{4}} dv = \ln|x| + C$$ Using substitution $u = 1-v^{4}$, $du = -4v^{3}dv$, the first part integrates to $-\frac{1}{4}\ln|1-v^{4}|$. The second part involves partial fractions or standard forms. Solving leads to: $$(x^{2}+y^{2})^{2} = C(x^{2}-y^{2})$$

Final Answer: (x^{2}+y^{2})^{2} = C(x^{2}-y^{2})

AI generated content. Review strictly for academic accuracy.

Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student must identify the homogeneous nature of the differential equation and apply the standard substitution method $y=vx$ to transform it into a separable form.
Knowledge Dimension: PROCEDURAL
Justification: The problem requires a multi-step algorithmic approach involving substitution, algebraic simplification, and integration techniques.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. It tests the student's ability to recognize and solve homogeneous differential equations, a core topic in the Calculus unit.