MCQ
The value of $\int_1^{{e^2}} {\frac{{dx}}{{x{{(1 + \ln x)}^2}}}} $ is
  • $2/3$
  • B
    $1/3$
  • C
    $3/2$
  • D
    $\ln 2$

Answer

Correct option: A.
$2/3$
a
(a) $I = \int_1^{{e^2}} {\frac{{dx}}{{x{{(1 + \ln x)}^2}}}} $

Let $(1 + \ln x) = t$ 

==> $dt = \frac{1}{x}dx$

Now, when $x = 1 \to {e^2}$, then $t = 1 \to 3$

$\therefore $ $I = \int_1^3 {\frac{{dt}}{{{t^2}}} = \left[ {\frac{{ - 1}}{t}} \right]_1^3= - \left[ {\frac{1}{3} - 1} \right]} = \frac{2}{3}$.

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