MCQ
The function $f(x) = \log (1 + x) - {{2x} \over {2 + x}}$ is increasing on
- ✓(0, $\infty $)
- B($ - \infty $, 0)
- C$( - \infty ,\infty )$
- DNone of these
$ \Rightarrow f'(x) = \frac{1}{{1 + x}} - \frac{{(2 + x).(2 - 2x)}}{{{{(2 + x)}^2}}}$
==> $f'(x) = \frac{{{x^2}}}{{(x + 1){{(x + 2)}^2}}}$
Obviously, $f'(x) > 0$ for all $x > 0$
Hence $f(x)$ is increasing on $(0,\infty )$.
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