MCQ
The solution of $(1 + xy)y\,dx + (1 - xy)x\,dy = 0$ is
  • A
    $\frac{x}{y} + \frac{1}{{xy}} = k$
  • $\log \left( {\frac{x}{y}} \right) = \frac{1}{{xy}} + k$
  • C
    $\frac{x}{y} + \frac{1}{{xy}} = k$
  • D
    $\log \left( {\frac{x}{y}} \right) = xy + k$

Answer

Correct option: B.
$\log \left( {\frac{x}{y}} \right) = \frac{1}{{xy}} + k$
b
(b) $ydx + xdy + x{y^2}dx - {x^2}ydy = 0$

$\frac{{ydx + xdy}}{{{x^2}{y^2}}} + \frac{{dx}}{x} - \frac{{dy}}{y} = 0$. On integrating, we get

$ - \frac{1}{{xy}} + \log x - \log y = k$ ==> $\log \frac{x}{y} = \frac{1}{{xy}} + k$.

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