For differential equation $y e^{\frac{x}{y}} dx = \left(x e^{\frac{x}{y}}+y^2\right)dy$, y(0) = 1, the value of x(e) is equal to : |
0 1 2 e |
e |
$y e^{\frac{x}{y}} dx = \left[x e^{\frac{x}{y}}+y^2\right]dy$ so $\frac{dx}{dy} = \left[\frac{x}{y} + \frac{y}{e^{\frac{x}{y}}} \right]$ so let x = vy $v + \frac{y ~dv}{dy} = v + \frac{y}{e^v}$ ⇒ $\frac{y dv}{dy} = \frac{y}{e^v}$ so $\int e^v dv = \int dy$ (integrating both sides) so ev = y + C so $e^{\frac{x}{y}} = y + C$ so x = y log(y + C) at x = 0 y = 1 so 0 = 1 log(1 + C) ⇒ log(1 + C) = 0 ⇒ log(1 + C) = log 1 ⇒ C = 0 so $x = y \log y$ at $x = e, y = e$ |