Gujarat BoardEnglish MediumSTD 12 ScienceMathsDifferential Equations1 Mark
MCQ
The general solution of the differential equation $x d y+y d x=0$ is:
✓
$x y=c$
B
$x+y=c$
C
$x^2+y^2=c^2$
D
$\log y=\log x+c$
✓
Answer
Correct option: A.
$x y=c$
We have, $x d y+y d x=0$
$\Rightarrow x d y=-y d x $
$\Rightarrow \int \frac{d y}{y}=-\int \frac{d x}{x} $
$\Rightarrow \log y=-\log x+\log c $
$\Rightarrow y=\frac{c}{x}$
$\Rightarrow x y=\text { constant }$
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