Let the solution curve of the differential equation x d y=(√(x^2+y^2)+y) d x, x>0, intersect the line x=1 at y=0 and the line x=2 at y=α. Then the…

Let the solution curve of the differential equation $\displaystyle x \mathrm{~d} y=\left(\sqrt{x^2+y^2}+y\right) \mathrm{d} x, x>0$, intersect the line $\displaystyle x=1$ at $\displaystyle y=0$ and the line $\displaystyle x=2$ at $\displaystyle y=\alpha$. Then the value of $\displaystyle \alpha$ is :