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MHT CET · Maths · Differential Equations

The differential equation of all parabolas having vertex at the origin and axis along positive \(\mathrm{Y}\)-axis is

  1. A \(x^2 \frac{d y}{d x}-y=0\)
  2. B \(x \frac{d y}{d x}+2 y=0\)
  3. C \(x \frac{d y}{d x}+y=0\)
  4. D \(2 x \frac{d y}{d x}-y=0\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(2 x \frac{d y}{d x}-y=0\)

Step-by-step Solution

Detailed explanation

We have \(y^2=4 a x\)
\(\therefore 2 y \frac{d y}{d x}=4 a \quad \Rightarrow a=\left(\frac{y}{2}\right) \frac{d y}{d x}\)
\(\therefore y^2=4\left(\frac{y}{2}\right)\left(\frac{d y}{d x}\right) x \Rightarrow y^2=2 x y \frac{d y}{d x}\)
\(\therefore 2 x \frac{d y}{d x}-y=0\)