MCQ
The solution of $\frac{{dy}}{{dx}} + y = {e^{ - x}},\,\,y(0) = 0$, is
  • A
    $y = {e^{ - x}}(x - 1)$
  • B
    $y = x{e^x}$
  • C
    $y = x{e^{ - x}} + 1$
  • $y = x{e^{ - x}}$

Answer

Correct option: D.
$y = x{e^{ - x}}$
d
(d) $\frac{{dy}}{{dx}} + y = {e^{ - x}}$; $I.F.$ $ = {e^{\int {dx} }} = {e^x}$

$y{e^x} = \int {{e^{ - x}}.{e^x}dx + c} $ ==> $y{e^x} = x + c$

Since $y(0) = 0$,  $c = 0$

Hence, the required solution is $y{e^x} = x$ ==> $y = x{e^{ - x}}$.

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