MCQ
$\int_0^1 {\frac{{dx}}{{{{[ax + b(1 - x)]}^2}}}} = $
  • A
    $\frac{a}{b}$
  • B
    $\frac{b}{a}$
  • C
    $a\,b$
  • $\frac{1}{{a\,b}}$

Answer

Correct option: D.
$\frac{1}{{a\,b}}$
d
(d) Let $I = \int_0^1 {\frac{{dx}}{{{{[(a - b)x + b]}^2}}}} $

Put $t = (a - b)x + b \Rightarrow dt = (a - b)dx$

As $x = 1 \Rightarrow t = a$ and $x = 0 \Rightarrow t = b$, then

$I = \frac{1}{{a - b}}\int_b^a {\frac{1}{{{t^2}}}} dt = \frac{1}{{(a - b)}}\left[ { - \frac{1}{t}} \right]_b^a $

$= \frac{1}{{(a - b)}}\left( {\frac{{a - b}}{{ab}}} \right) = \frac{1}{{ab}}$.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free