MCQ
Let $f: \rightarrow R \rightarrow(0, \infty)$ be strictly increasing function such that $\lim _{x \rightarrow \infty} \frac{f(7 x)}{f(x)}=1$. Then, the value of $\lim _{x \rightarrow \infty}\left[\frac{f(5 x)}{f(x)}-1\right]$ is equal to
  • A
    $4$
  • $0$
  • C
    $7 / 5$
  • D
    $1$

Answer

Correct option: B.
$0$
b
$ f: R \rightarrow(0, \infty)$

$ \lim _{x \rightarrow \infty} \frac{f(7 x)}{f(x)}=1 $

$ \because \mathrm{f} \text { is increasing } $

$ \therefore \mathrm{f}(\mathrm{x})<\mathrm{f}(5 \mathrm{x})<\mathrm{f}(7 \mathrm{x})$

$ \because \frac{f(x)}{f(x)}<\frac{f(5 x)}{f(x)}<\frac{f(7 x)}{f(x)}$

$ 1<\lim _{x \rightarrow \infty} \frac{f(5 x)}{f(x)}<1 $

$ \therefore\left[\frac{\mathrm{f}(5 \mathrm{x})}{\mathrm{f}(\mathrm{x})}-1\right] $

$ \Rightarrow 1-1=0 $

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