MCQ
$\int_{}^{} {\frac{{a\;dx}}{{b + c{e^x}}}} = $
  • $\frac{a}{b}\log \left( {\frac{{{e^x}}}{{b + c{e^x}}}} \right) + c$
  • B
    $\frac{a}{b}\log \left( {\frac{{b + c{e^x}}}{{{e^x}}}} \right) + c$
  • C
    $\frac{b}{a}\log \left( {\frac{{{e^x}}}{{b + c{e^x}}}} \right) + c$
  • D
    $\frac{b}{a}\log \left( {\frac{{b + c{e^x}}}{{{e^x}}}} \right) + c$

Answer

Correct option: A.
$\frac{a}{b}\log \left( {\frac{{{e^x}}}{{b + c{e^x}}}} \right) + c$
a
(a)$\int_{}^{} {\frac{{a\,dx}}{{b + c\,{e^x}}} = \int_{}^{} {\frac{{a{e^x}}}{{b{e^x} + c\,{e^{2x}}}}\,dx} } $
Now put ${e^x} = t,$ then it reduces to
$a\int_{}^{} {\frac{{dt}}{{t(ct + b)}} = a\int_{}^{} { - \frac{1}{b}\left\{ {\frac{c}{{ct + b}} - \frac{1}{t}} \right\}dt} } $ {By partial fraction}
$ = \frac{a}{b}\log \left( {\frac{{{e^x}}}{{b + c{e^x}}}} \right) + c$.

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