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CUET · MATHS · PYQ PAPER 2023

The differential equation of the family of parabolas \(y^2=4 a x\) where \(a\) is an arbitrary constant is :

  1. A \(2 x \frac{d y}{d x}=y\)
  2. B \(x \frac{d y}{d x}=y\)
  3. C \(y \frac{d y}{d x}=\frac{x}{2}\)
  4. D \(2 y \frac{d y}{d x}=x^2\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(2 x \frac{d y}{d x}=y\)

Step-by-step Solution

Detailed explanation

\(y^2 = 4ax\) \(2y \frac{dy}{dx} = 4a\) \(a = \frac{y}{2} \frac{dy}{dx}\) \(y^2 = 4 \left( \frac{y}{2} \frac{dy}{dx} \right) x\) \(y^2 = 2yx \frac{dy}{dx}\) \(y = 2x \frac{dy}{dx}\) \(2x \frac{dy}{dx} = y\)