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JEE Mains · Maths · STD 12 - 6. Application of derivatives

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

  1. A \(4\)
  2. B \(0\)
  3. C \(7 / 5\)
  4. D \(1\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(0\)

Step-by-step Solution

Detailed explanation

\( f: R \rightarrow(0, \infty)\) \( \lim _{x \rightarrow \infty} \frac{f(7 x)}{f(x)}=1 \) \( \because \mathrm{f} \text { is increasing } \) \( \therefore \mathrm{f}(\mathrm{x})<\mathrm{f}(5 \mathrm{x})<\mathrm{f}(7 \mathrm{x})\)…