MCQ
Choose the correct answer from the given four option. Solution of differential equation $x\ dy - y \ dx = 0$ represents :
  • A
    A rectangular hyperbola.
  • B
    Parabola whose vertex is at origin.
  • Straight line passing through origin.
  • D
    A circle whose centre is at origin.

Answer

Correct option: C.
Straight line passing through origin.
Given that, $\text{x dy}-\text{y dx}=0$
$\Rightarrow\text{x dy}=\text{y dx}$
$\Rightarrow\frac{\text{dy}}{\text{y}}=\frac{\text{dx}}{\text{x}}$
On integrating both sides, we get
$\Rightarrow\int\frac{\text{dy}}{\text{y}}=\int\frac{\text{dx}}{\text{x}}$
$\Rightarrow\log\text{y}=\log\text{x}+\log\text{C}$
$\Rightarrow\log\text{y}=\log\text{Cx}$
$\Rightarrow\text{y}=\text{Cx}$
Which is a straight line passing through origin.

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