The differential equation of an ellipse whose major axis is twice its minor axis, is

The differential equation of an ellipse whose major axis is twice its minor axis, is
  1. $x+4 y \frac{d y}{d x}=0$
  2. $x-4 y \frac{d y}{d x}=0$
  3. $x+2 y \frac{d y}{d x}=0$
  4. None of these

Solution

For the given ellipse, we have $\mathrm{a}=2 \mathrm{~b}$ $\therefore \therefore \frac{\mathrm{x}^2}{4 \mathrm{~b}^2}+\frac{\mathrm{y}^2}{\mathrm{~b}^2}=1 \Rightarrow \mathrm{x}^2+4 \mathrm{y}^2=4 \mathrm{~b}^2$ Differentiating both sides w.r.t., we get $2 x+8 y \frac{d y}{d x}=0 \Rightarrow x+4 y \frac{d y}{d x}=0$

Asked in: MHT CET 2021 (20 Sep Shift 2)

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