Solve this following

Question:

Let $y=y(x)$ be the solution of the differential equation $d y=e^{\alpha x+y} d x ; \alpha \in \mathbf{N}$. If $y\left(\log _{e} 2\right)=\log _{e} 2$ and $y(0)=\log _{e}\left(\frac{1}{2}\right)$, then the value of $\alpha$ is equal

to______________

Solution:

$\int e^{-y} d y=\int e^{\alpha x} d x$

$\Rightarrow \mathrm{e}^{-\mathrm{y}}=\frac{\mathrm{e}^{\alpha \mathrm{x}}}{\alpha}+\mathrm{c}$ .......(I)

Put $(\mathrm{x}, \mathrm{y})=(\ln 2, \ell \mathrm{n} 2)$

$\frac{-1}{2}=\frac{2^{\alpha}}{\alpha}+C$  ..............(II)

Put $(\mathrm{x}, \mathrm{y}) \equiv(0,-\ell \mathrm{n} 2)$ in (I)

$-2=\frac{1}{\alpha}+C$  ...................(III)

(ii) - (iii)

$\frac{2^{\alpha}-1}{\alpha}=\frac{3}{2}$

$\Rightarrow \alpha=2($ as $\alpha \in \mathbb{N})$

 

 

Leave a comment

Close

Click here to get exam-ready with eSaral

For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.

Download Now