The differential equation of all family of lines $y=m x+\frac{4}{m}$ obtained by eliminating the arbitrary…

The differential equation of all family of lines $y=m x+\frac{4}{m}$ obtained by eliminating the arbitrary constant $\mathrm{m}$ is
  1. $y\left(\frac{d y}{d x}\right)=4$
  2. $y\left(\frac{d y}{d x}\right)^2+y\left(\frac{d y}{d x}\right)+4=0$
  3. $x\left(\frac{d y}{d x}\right)+4=0$
  4. $x\left(\frac{d y}{d x}\right)^2-y\left(\frac{d y}{d x}\right)+4=0$

Solution

$\begin{aligned} & y=m x+\frac{4}{m} \\ & \therefore \frac{d y}{d x}=m \end{aligned}$ Substituting value of $\mathrm{m}$ in equation (1), we get $\begin{aligned} & y=\left(\frac{d y}{d x}\right) x+\frac{4}{\left(\frac{d y}{d x}\right)} \\ & \therefore y\left(\frac{d y}{d x}\right)=\left(\frac{d y}{d x}\right)^2 x+4 \end{aligned}$

Asked in: MHT CET 2021 (22 Sep Shift 1)

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