If $\mathrm{f}(x)=\log _{\mathrm{c}}\left(\frac{1-x}{1+x}\right),|x| \lt 1$, then $\mathrm{f}\left(\frac{2…
If $\mathrm{f}(x)=\log _{\mathrm{c}}\left(\frac{1-x}{1+x}\right),|x| \lt 1$, then $\mathrm{f}\left(\frac{2 x}{1+x^2}\right)$ is equal to
- $2 \mathrm{f}\left(x^2\right)$
- $(\mathrm{f}(x))^2$
- $\quad-2 \mathrm{f}(x)$
- $2 \mathrm{f}(x)$
Solution
$\begin{aligned} f\left(\frac{2 x}{1+x^2}\right) & =\log _{\mathrm{e}}\left(\frac{1-\frac{2 x}{1+x^2}}{1+\frac{2 x}{1+x^2}}\right) \\ & =\log _{\mathrm{e}}\left(\frac{(1-x)^2}{(1+x)^2}\right) \\ & =2 \log _{\mathrm{e}}\left(\frac{1-x}{1+x}\right) \\ & =2 \mathrm{f}(x)\end{aligned}$
Asked in: MHT CET 2024 (04 May Shift 1)
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