MCQ
Solution of $(x + y - 1)dx + (2x + 2y - 3)dy = 0$ is
- A$y + x + \log (x + y - 2) = c$
- B$y + 2x + \log (x + y - 2) = c$
- ✓$2y + x + \log (x + y - 2) = c$
- D$2y + 2x + \log (x + y - 2) = c$
Put $x + y = t$ ==> $\frac{{dy}}{{dx}} = \frac{{dt}}{{dx}} - 1$
$\therefore \frac{{dy}}{{dx}} = \frac{{1 - t}}{{2t - 3}}$ ==> $\frac{{dt}}{{dx}} - 1 = \frac{{1 - t}}{{2t - 3}}$ ==> $\frac{{dt}}{{dx}} = \frac{{t - 2}}{{2t - 3}}$
==> $\frac{{2t - 3}}{{t - 2}}dt = dx$. Integrating both sides, we get
$\int_{}^{} {\frac{{2t - 4}}{{t - 2}}dt} - \int_{}^{} {\frac{{3 - 4}}{{t - 2}}dt} = \int_{}^{} 1 dx$
==> $2t + \log (t - 2) = x + c$
==> $2(x + y) + \log (x + y - 2) = x + c$
==> $2y + x + \log (x + y - 2) = c$.
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2
3
$-\frac{3}{2}$
None of these