CUET · MATHS · PYQ PAPER 2025

For the differential equation \(x \frac{d y}{d x}+2 y=x^2 \log _e x\)
(A) Integrating factor is \(2 x\)
(B) Integrating factor is \(x^2\)
(C) General Solution is \(y=\frac{x^2}{16}\left(4 \log _e|x|-1\right)+C x^{-2}\), where \(C\) is an arbitrary constant.
(D) General Solution is \(y=\frac{x^4}{16}\left(4 \log _e|x|-1\right)+C\), where \(C\) is an arbitrary constant.
Choose the correct answer from the options given below :

A (A) and (C) only
B (B) and (D) only
C (B) and (C) only
D (A) and (D) only

Verified Solution

Answer & Solution

Correct Answer

(C) (B) and (C) only

Step-by-step Solution

Detailed explanation

\(x \frac{d y}{d x}+2 y=x^2 \log _e x \implies \frac{d y}{d x}+\frac{2}{x} y=x \log _e x\) \(P(x) = \frac{2}{x}\) \(IF = e^{\int \frac{2}{x} dx} = e^{2 \log_e |x|} = e^{\log_e x^2} = x^2\) Therefore, option (B) is correct. \(y \cdot IF = \int (Q(x) \cdot IF) dx + C\)…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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