Let y = y(x) be the solution of the differential equation dy = e$\alpha$x + y dx; $\alpha$ $\in$ N. If y(loge2) = loge2 and y(0) = loge$\left( {{1 \over 2}} \right)$, then the value of $\alpha$ is equal to _____________.
Answer (integer)
2
Solution
$\int {{e^{ - y}}} dy = \int {{e^{\alpha x}}} dx$<br><br>$\Rightarrow {e^{ - y}} = {{{e^{\alpha x}}} \over \alpha } + c$ ..... (i)<br><br>Put (x, y) = (ln2, ln2)<br><br>${{ - 1} \over 2} = {{{2^\alpha }} \over \alpha } + C$ ..... (ii)<br><br>Put (x, y) $\equiv$ (0, $-$ln2) in (i)<br><br>$- 2 = {1 \over \alpha } + C$ ..... (iii)<br><br>(ii) $-$ (iii)<br><br>${{{2^\alpha } - 1} \over \alpha } = {3 \over 2}$<br><br>$\Rightarrow$ $\alpha$ = 2 (as $\alpha$ $\in$ N)
About this question
Subject: Mathematics · Chapter: Differential Equations · Topic: Order and Degree
This question is part of PrepWiser's free JEE Main question bank. 172 more solved questions on Differential Equations are available — start with the harder ones if your accuracy is >70%.