MCQ
જો $f(x) = \frac{x}{{1 + x}}$, તો ${f^{ - 1}}(x) =$
  • A
    $\frac{{(1 + x)}}{x}$
  • B
    $\frac{1}{{(1 + x)}}$
  • C
    $\frac{{(1 + x)}}{{(1 - x)}}$
  • $\frac{x}{{(1 - x)}}$

Answer

Correct option: D.
$\frac{x}{{(1 - x)}}$
d
(d) $f(x) = \frac{x}{{1 + x}}$. Let $y = f(x) \Rightarrow x = {f^{ - 1}}(y)$

$\therefore$ $y = \frac{x}{{1 + x}} \Rightarrow y + yx = x$

==> $x = \frac{y}{{1 - y}}$

==> ${f^{ - 1}}(y) = \frac{y}{{1 - y}}$

==> ${f^{ - 1}}(x) = \frac{x}{{1 - x}}$.

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