The equation of a curve passing through the origin and satisfying the differential equation $\frac{d y}{d x}=(x-y)^2$, is
Answer & explanation
Correct answer: option 1
We have, $\frac{d y}{d x}=(x-y)^2$
Let $x-y=v$. Then,
$1-\frac{d y}{d x}=\frac{d v}{d x} \Rightarrow \frac{d y}{d x}=1-\frac{d v}{d x}$
∴ $\frac{d y}{d x}=(x-y)^2$
$\Rightarrow 1-\frac{d v}{d x}=v^2$
$\Rightarrow 1-v^2 = \frac{d v}{d x}$
$\Rightarrow d x=\frac{1}{1-v^2} d v$
$\Rightarrow 2 \int d x=2 \int \frac{1}{1-v^2} d v$
$\Rightarrow 2 x=\log \left(\frac{1+v}{1-v}\right)+\log C$
$\Rightarrow C\left(\frac{1+v}{1-v}\right)=e^{2 x}$
$\Rightarrow C\left(\frac{x-y+1}{y-x+1}\right)=e^{2 x} \Rightarrow C(x-y+1)=e^{2 x}(y-x+1)$
Taking $C=1$, we find that option (a) is correct.