MCQ
The solution of ${e^{dy/dx}} = (x + 1)$, $y(0) = 3$ is
  • A
    $y = x\log x - x + 2$
  • $y = (x + 1)\log |x + 1| - x + 3$
  • C
    $y = (x + 1)\log |x + 1| + x + 3$
  • D
    $y = x\log x + x + 3$

Answer

Correct option: B.
$y = (x + 1)\log |x + 1| - x + 3$
b
(b) $\frac{{dy}}{{dx}} = \log (x + 1)$ ==> $dy = \log (x + 1)dx$

$y = \int {\log (x + 1)dx} = x.\log (x + 1) - \int {\frac{x}{{x + 1}}dx} $

$ = x.\log (x + 1) - \int {\left( {1 - \frac{1}{{x + 1}}} \right)} \,dx$

$ = x.\log (x + 1) - x + \log (x + 1) + c$

$ = (x + 1)\log (x + 1) - x + c$

$x = 0$ at $y = 3$

$3 = (1)\log (1) - 0 + c$ ==> $3 = 0 + c$ ==> $c = 3$

 $y = (x + 1)\log |x + 1| - x + 3$.

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